Questions:
- What is SCSI?
- What is the SCSI Trade Association (STA)?
- What is Wide SCSI?
- What is FAST SCSI-2?
- What is Ultra SCSI?
- What is Ultra-2 SCSI?
- What is SCSI Ultra-3?
- What is Ultra-160?
- I get a "NO ROM BASIC" message when trying to boot from my SCSI hard drive.
- There are two places to configure SCSI hard drive features and options (Set SCSI ID, Termination Power, Force Single Ended mode, etc) Which jumper terminal block do I use?
- What is Termination?
- What is passive termination?
- What is active termination?
- If I set termination on the host adapter to Automatic, do I still need to terminate the SCSI devices?
- What is parity?
- An LVD drive is not seen during a Windows NT 4.0 installation, when the LVD drive is connected to an embedded host adapterSingle Ended devices may be seen, but not the LVD driveWhy?
- What is the difference between Asynchronous and Synchronous SCSI?
- If my hard drive passes all the SCSI tests, but I still cannot run a program, or access a file on my system, what should I do?
- Why does my SCSI hard drive report less capacity than indicated on the drive?
- SCSI hard drives greater than 2.1 GB are not recognized at full capacity. Why?
- What is the difference between "hot swap" and "hot spare"?
- What do the terms Single Ended and Differential mean?
- What is an "No ROM Basic" error?
- High Voltage Differential (HVD) SCSI hard drive compatibility issue.
What is the difference between a Quick Media Scan and a Full Surface Scan?
- What does the term LVD mean?
- How can I tell if my SCSI drive is Apple Macintosh compatible?
- How Does Ultra DMA Compare With Ultra SCSI Controllers?
- My SCSI host adapter is not identified by the operating system. Do I need a software driver for the operating system?
- FDISK does not report the correct size for a SCSI hard drive larger than 64 GB. Why?
- "Not enough drive letters" error.
What are the parameters I put in CMOS (BIOS setup) for my SCSI hard drive?
- I have a PCI SCSI RAID controller and the drives go offline during heavy loads. Why?
- Can I boot my from my SCSI hard drive?
- Can I boot from my SCSI hard drive with an IDE/EIDE drive installed?
- Sustained data transfer rates for SCSI hard drives issue.
I have a SCSI RAID controller and the drives keep coming up marked dead/off-lineI can return the drives on-line again, but why is this happening and what can I do to fix it?
- Where to locate ASPI drivers for SCSI host adapters?
- My SCSI hard drive doesn't spin up when I apply power to it. What's wrong?
- If my hard drive only fails on the manufacturer’s SCSI diagnostic tests, does this mean that it is defective and should be returned?
- Will SCSI performance suffer if I attach more than one drive to my controller?
- Potential problem with LVD termination and the Adaptec 2940U2/W.
Should I update the BIOS on my SCSI controller? And if so, how would I do this?
- SCSI Cable and Termination issues.
Can I use a standard 68-pin ribbon cable with an Ultra2 SCSI installation?
- My SCSI hard drive runs hot - Ventilation guidelines for high speed SCSI disk drives.
- My SCSI hard drive will not boot. What's wrong?
- How do I perform basic troubleshooting for a SCSI hard drive in an Apple Macintosh?
- Can I use Apple's Drive Setup to initialize and partition my new SCSI drive?
- Do I need CHS parameters (Cylinders, Heads, and Sectors) for my SCSI hard drive?
- Excessive heat and high-speed SCSI hard drives issues.
My SCSI hard drive runs slow during start up, running applications, or accessing dataWhat’s wrong?
- Why is the hard disk drive NOT as fast as advertised?
- How do I make my SCSI hard drive a master or slave?
- System hangs when using SCA-2 pin converter or interface adapter.
How do I properly terminate a LVD (Low Voltage Differential) SCSI hard drive?
- Can't partition a SCSI hard drive with FDISKWhat happens?
- What is the SCA interface?
- How can an SCA interface drive be attached to a standard 50-pin or 68-pin SCSI host adapter?
Answers:
What is SCSI? SCSI stands for Small Computer System Interface. It was originally derived from SASI (Shugart Associates System Interface) as an attempt to come up with an intelligent, non-device specific bus to connect peripherals to a PC. Currently, SCSI allows for up to fifteen devices in series (plus controller) and each is assigned a unique SCSI ID from 0 to 15. Each of those devices can in turn address up to 64 logical units (LUN - or Logical Unit Number), although a hard drive will typically have only one LUN. SCSI is considered a `negative bus' which means all signals are negated by being pulled or driven high and are asserted by being driven low. Due to the large number of devices SCSI is capable of addressing, the bus must be terminated.
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What is the SCSI Trade Association (STA)? The SCSI Trade Association, or STA, was formed in 1995 to promote the use and understanding of small computer system parallel interface technology, to provide a focal point for communicating SCSI benefits, and to influence the evolution of SCSI into the future.
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What is Wide SCSI? Wide SCSI is a way to double the bus width, or number of data bits that can be transferred in a single clock cycle. To accomplish this, Wide SCSI uses a 68-pin cable, sometimes called a 'P' cable, capable of transferring data at 16 bits (2 Bytes) at a time compared to 8 bits (1 Byte) for a Narrow (50-pin) bus. As with narrow SCSI, Wide SCSI is available as Single-Ended, Differential, and Low Voltage Differential (LVD). Wide SCSI is capable of addressing up to 16 SCSI ID's (typically one controller and 15 devices).
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What is FAST SCSI-2? FAST SCSI-2 refers to the effective doubling of the bandwidth SCSI-1 is capable of transmitting by increasing the frequency of the signals from 5 MHz to 10 MHz. The maximum data transfer rate across the bus is 10MB/Sec on a Narrow bus, and 20MB/Sec on a Wide bus.
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What is Ultra SCSI? Fast-20, known as Ultra SCSI, is a method for bus-speed doubling as defined in the SPI (SCSI Parallel Interface) document. Ultra SCSI allows 20 megabyte per second or on a wide bus (16 bit data path), 40 megabytes per second. This is not the complete standard. It only has the sections required for the Fast-20 protocols, all other sections use the SPI standard. (Fast-20 became a standard approximately 1996, Obsolete July 1999, use SPI-2)
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What is Ultra-2 SCSI? Ultra 2-SCSI, also at times referred to as Ultra LVD, is the STA’s definition for Fast-40. Fast-40 refers to the SCSI bus data transfer rate of 80MB/s (max) on a wide bus. In order to achieve the 80MB/s transfer rate, devices must run in LVD mode.
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What is SCSI Ultra-3? The SCSI Ultra-3 standards comprise a set of core technologies: Cyclical Redundancy Checking (CRC), Domain Validation, and Double Edge Clocking. To call a product "Ultra-3 compliant", any one or all of these embedded technologies can be used. The SCSI standard is clearly defined, and Ultra-160 and Ultra-3 SCSI devices are compatible with one another. SCSI technology has for many years maintained its core value by offering enhanced performance with complete backward compatibility in every generation of technology.
This is especially true with the latest generation of SCSI, called Ultra-160 and Ultra-3 SCSI. Although some SCSI vendors have chosen to name their implementation with a slight twist in the name, the promise of compatibility is maintained in all such variations. In other words not only will all flavors of Ultra-160 and Ultra-3 SCSI work with older generations of SCSI, all Ultra-160 and Ultra-3 devices are inter-operable irrespective of the name used by its vendor. Ultra-3 SCSI encompasses any or all of the five features in the specification. Several SCSI vendors subsequently defined Ultra-160 SCSI as a specific implementation of three of the five Ultra-3 SCSI features. These three core features are double edge clocking, cyclical redundancy checking (CRC) and domain validation. To date, every vendor that has announced a new generation SCSI product, whether under the Ultra-3 or Ultra-160 name, has included these three core features.
Several vendors use a modified Ultra-160 SCSI name, such as Ultra-160+, for their latest SCSI technology. These vendors have added a feature to the set of three core features in order to differentiate their products. However, all of the implementations, regardless of what they're called, and regardless of whether or not they have an additional feature, support the three core features defined in the current SCSI specification. The name Ultra-160 SCSI is now recognized by the industry's SCSI Trade Association (STA) to identify designs with these three key features. The association has further added credibility to the naming by establishing Ultra-320 and Ultra-640 as the names for future generations of SCSI technology. Each of these generations is expected to have a specific set of feature enhancements and are also expected to offer full backward compatibility with prior generations of SCSI.
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What is Ultra-160? See "what is Ultra-3".
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I get a "NO ROM BASIC" message when trying to boot from my SCSI hard drive.
Reboot your system from your DOS diskette, run the FDISK program and make sure the primary partition on the first hard drive (your `C' drive) is set active. Also make sure the boot files have been copied to the hard disk, by using the /S switch when formatting, or using the SYS command to copy the necessary files over.
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There are two places to configure SCSI hard drive features and options. (Set SCSI ID, Termination Power, Force Single Ended mode, etc). Which jumper terminal block do I use? A SCSI hard drive may be configured in a variety of ways. Two locations for drive options maximize versatility. The larger 28-pin option connector will override any settings on the smaller 12-pin connector. OEM manufacturers and system integrators often use the smaller terminal block for cable harnesses to control drive options.
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What is Termination? Termination means that special electrical resistors (terminators) are installed in the devices at each end of the bus and are not installed in other devices on the bus. With some SCSI devices you must manually insert or remove the terminators. Many devices have built-in terminators that are enabled or disabled via switches or software commands. LVD drives do not supply on board termination, and the SCSI bus must be terminated by other means, such as LVD/SE cable terminators.
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What is passive termination? Passive termination utilizes a 220/330-ohm resistor network to provide the necessary impedance on the cable to prevent data from reflecting back. Passive termination draws its power from the SCSI controller host - such that any fluctuations in Termination Power as supplied from the host, will result in fluctuations on the data lines. This may sometimes lead to errors in the data, and is not recommended for Fast SCSI (10 MBytes/Sec. Max) or faster (Ultra2, Ultra3, Ultra320) SCSI buses.
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What is active termination? Active termination utilizes a 110-ohm resistor on each signal line - which in turn connects to a voltage regulator to prevent data from 'reflecting' back. With active termination the voltage is kept at a constant 2.85V, active termination is less prone to power fluctuations than passive termination which gets power from the host. Active termination is recommended for systems operating at Fast-SCSI or higher bus rates.
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If I set termination on the host adapter to Automatic, do I still need to terminate the SCSI devices? Setting the host adapter to Automatic termination, allows the SCSI controller to enable/disable termination without user intervention. However, this setting applies only to the termination on the host adapter, and not to any SCSI devices attached to the adapter. Devices at the physical end of the internal or external cable must still be terminated properly. An external active (system) terminator is the best method to terminate SCSI Low Voltage Differential (LVD) devices.
Automatic Termination can be a useful feature when an external device such as a tape drive, scanner, or external hard drive, is shared between computer systems. The SCSI host adapter will correctly terminate itself as the cable for the external device is connected or removed, without the user having to reconfigure or gain access to the SCSI controller. Refer to your system or SCSI controller documentation regarding any specific recommendations regarding drive placement on the SCSI bus and SCSI bus termination.
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What is parity? Parity is a way of detecting transmission errors, performed as the data is being sent across the SCSI bus. There are two types of parity: odd and even parity checking. SCSI uses odd parity checking such that the number of logical 1's in a given bit should always result in an odd number. If it doesn't, the device knows that an error has occurred and requests that the data be re-sent.
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An LVD drive is not seen during a Windows NT 4.0 installation, when the LVD drive is connected to an embedded host adapter. Single Ended devices may be seen, but not the LVD drive. Why? The NT 4.0 installation CDROM does not directly support the ADAPTEC AIC-7890 chipset (or the AHA2940U2W). The user will need to provide a driver for this host adapter. Adaptec provides this driver for customers at its web site. Once the driver is loaded, the user should be able to see both the AIC-7890 (and AHA2940U2W) and the LVD devices attached to the host. This problem is more common with the embedded host adapter since many systems with the AIC-7890 also have a second host adapter for the Single-Ended (SE) devices.
The user is able to see the SE devices, but not the LVD drives. If this is observed, have the user reboot the system and confirm that the system is performing two SCSI bus scans, one for each host adapter, and inform them that they will need to provide a driver for the LVD host adapter, since NT does not. This is done during the NT installation when the system asks if you would like to specify additional devices. The user can also install NT on the SE devices, and add this driver afterwards, via the Control Panel, to see the drive.
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What is the difference between Asynchronous and Synchronous SCSI? SCSI data is sent using a series REQuests and ACKnowledgements, or REQs and ACKs. When data is sent Asynchronously, each REQ must receive an ACK before the next signal is sent. All commands are sent Asynchronously over the 8-bit bus. When data is transferred Synchronously, multiple REQs can be issued, up to the maximum offset (number of outstanding REQs), and then wait for the corresponding number of ACKs to be returned. Using Synchronous transfers can greatly improve throughput.
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If my hard drive passes all the SCSI tests, but I still cannot run a program, or access a file on my system, what should I do?
If the disk drive passes all tests; the problem remains somewhere else in your system. You could have a system hardware problem or a corrupted file. You might try reloading the operating system or application program software. You could also try other utilities that go beyond the hard drive to test for viruses, file system problems, and registry integrity. SCSI, ATA, 1394 and USB2 diagnostic utilities for Apple and Microsoft platforms are available from these and many other manufacturers:
www.reynolds-data.com
www.symantec.com
www.Ontrack.com
www.scsitools.com
www.charismac.com
www.fwb.com
www.recallusa.com
www.micromat.com
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Why does my SCSI hard drive report less capacity than indicated on the drive? Hard drives are marketed in terms of decimal (base 10) capacity. In decimal notation, one megabyte (MB) is equal to 1,000,000 bytes, and one Gigabyte (GB) is equal to 1,000,000,000 bytes. However, computers (and programs such as FDISK) use the binary (base 2) numbering system. In the binary numbering system, one megabyte is equal to 1,048,576 bytes, and one gigabyte is equal to 1,073,741,824 bytes. DOS FDISK and Apple's operating system (MAC O/S) use the binary numbering system. When determining hard drive capacities with FDISK, one should multiply the value shown in FDISK (displayed in base 2 megabytes) by 1,048,576 to determine the decimal equivalent for the hard drive's capacity.
For example, you run FDISK and it displays the capacity of your hard drive as 8678 Megabytes. This value represents the base 2 or binary capacity of the disk drive. To determine the equivalent base 10 or decimal capacity, multiply 8678 by 1,048,576. This results in a value of 9,099,542,528 bytes or approximately 9.1GB in decimal terms.
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SCSI hard drives greater than 2.1 GB are not recognized at full capacity. Why? Using older SCSI controllers and operating systems, hard drives greater than 2.1 GB are not recognized at true capacity. This is usually due to logical addressing constraints and operating system support for large capacity hard drives. See your system (board) manufacturer or SCSI controller vendor, for a system BIOS or ASPI driver update. If this is not an option, upgrade the SCSI controller or system (board).
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What is the difference between "hot swap" and "hot spare"? "Hot Swap" is the ability of a SCSI RAID controller's software suite to allow removal and replacement of a disk drive while users are on-line and accessing data (active I/O). All hot swap, hot spare disk drives are sold in 80-pin SCA-2 SCSI interface configurations. Hard drives and enclosures must be compatible with Hot Swap level-4 compliance. "Hot Spare" is a RAID architecture feature to allow an extra hard drive to be included on a RAID controller, in case of sudden drive failure. By definition, the spare device, is not pre-configured as part of the RAID array. The spare drive is available to automatically reconstruct data in the event any single drive fails during normal system function.
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What do the terms Single Ended and Differential mean? On a Single-Ended device, one line defines one bit. A high (or negated) signal denotes a logical zero, a low (or asserted) signal denotes a logical one. In a Differential device, two lines, instead of one are used to define a bit. The information is defined as the difference between the two signals (which are referred simply as + and - ) and not just the voltage level of a single line. Since the differential between two lines is used, (hence the name) this type of SCSI is more robust than Single-Ended and can travel longer distances without noticeable signal degradation. Though both Differential and Single-Ended devices use the same connectors, they are electrically different and require different types of host adapters.
High Voltage Differential devices will not work with Single-Ended host adapters and vice-versa. Differential (High Voltage Differential) drives and LVD (Low Voltage Differential) drives differ from each other. The most notable difference is that LVD drives can work on Single Ended host adapter, and likewise, an LVD host adapter can work with Single Ended drives, though mixing Single Ended devices with LVD device on the same cable will result in the entire cable operating in Single Ended mode.
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What is an "No ROM Basic" error? When a partition is not set to the bootable partition. This usually occurs when the drive at one time was a slave and now has moved into the primary position. Verify that the hard drive has an "Active/Primary" DOS partition. This can be accomplished with the DOS FDISK utility. Boot your system with DOS system diskette, type "FDISK/MBR" and press [Enter].
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High Voltage Differential (HVD) SCSI hard drive compatibility issue.
HVD drives are not compatible with SCSI single ended (SE) or Low Voltage differential (LVD) devices. Both differential and single-ended devices use the same connectors, but are electrically different and require different types of SCSI controllers. Differential devices will not work with single-ended controllers and vice-versa. Please note that HVD and LVD drives do not provide active SCSI bus termination. Do not install differential drives at the end of the SCSI bus unless the bus is properly terminated by an external (cable end) active terminator resistor circuit. Otherwise, proper operation of the bus cannot be assured. Refer to your computer system or SCSI controller documentation for recommendations on drive placement and bus termination. You may consider the purchase of an HVD SCSI controller. Adaptec, ATTO, DPT, Mylex, Symbios, are only a few of the available SCSI controller vendors.
What is the difference between a Quick Media Scan and a Full Surface Scan? Quick Media Scan checks only the critical areas of the hard drive, approximately the first 300 MB and the last 100 MB of a drive. The first 300 MB is where the operating system and critical files are usually stored. The last 100 MB is typically where most errors occur as a result of shipping or handling damage. The Quick Scan takes approximately two minutes to complete. The Full Surface Scan checks the entire hard drive so the length of the test will vary depending on the drive's capacity. The average run time for a 9GB drive under the Full Scan is approximately 15 minutes.
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What does the term LVD mean? LVD stands for Low Voltage Differential (sometimes called Multi-Mode LVD). Similar to Differential (HVD), in that two lines (a "+" and "-" signal) are used to define any given signal, LVD is different than High Voltage Differential in two respects: LVD uses lower voltage levels than HVD, and LVD devices can operate on a Single-Ended bus and Vice Versa. However, the presence of any Single-Ended device on an LVD cable will force all devices on that cable to operate in Single-Ended mode. HVD SCSI devices cannot be used on the same SCSI cable with either Single-Ended or LVD devices and require the use of a HVD SCSI controller.
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How can I tell if my SCSI drive is Apple Macintosh compatible?
Most SCSI drives will work in an Apple computer. Third party installation software is often needed to identify the drive to the MAC operating software. For software driver support, contact your local computer dealer or APPLE reseller details on available software programs. The following companies develop APPLE hard drive formatting and diagnostic tools:
The La Cie Storage Utilities (AKA: Silver Lining)
Telephone:
503-844-4500
Internet: http://www.lacie.com/
FWB Software's Hard Disk Toolkit
Telephone:
650-482-4800
Internet: http://www.fwb.com/
Micromat Inc. TechTool Pro & Drive 10
Telephone:
800-829-6227
Internet: http://www.micromat.com
CharisMac Engineering Inc. 'Anubis' utility
Telephone:
530-885-4420
Internet: http://www.charismac.com/
Symantec Inc. Norton Utlities for Macintosh
Telephone:
541-335-7000
Internet: http://www.symantec.com/
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How Does Ultra DMA Compare With Ultra SCSI Controllers? Ultra DMA has tested faster than Ultra Wide SCSI under WinMark97. User's can anticipate the high performance of Ultra DMA at half the price of SCSI.
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My SCSI host adapter is not identified by the operating system. Do I need a software driver for the operating system? SCSI hard drives do not need software drivers. Instead, the host adapter needs a driver to identify the attached devices to the operating system. The operating system installation disks or CD-ROM contain (ASPI) drivers for most commonly available host adapters. However, many newer host adapters, especially LVD (SCSI Low Voltage Differential hosts, may require separate drivers provided by the host adapter manufacturer. In cases where the host adapter is embedded in the motherboard, the motherboard manufacturer normally provides these drivers. Please contacting the host adapter manufacturer (or for embedded hosts, the motherboard manufacturer) for these drivers.
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FDISK does not report the correct size for a SCSI hard drive larger than 64 GB. Why? FDISK.EXE uses some 16-bit values internally to calculate the size of the drive. Some of these variables overflow when the drive size is larger than or equal to 64 GB. Microsoft ScanDisk also has limited support for high capacity hard drives too. A supported fix is available from Microsoft. Download the software patch from Microsoft Q#263044.
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"Not enough drive letters" error.
After adding a new device such as a hard drive or CD-ROM drive the system reports an error saying: "Not enough drive letters" or "Not enough drive letters available". This issue is caused by the "LASTDRIVE" line not setup properly or defined in the config.sys file. You must edit your CONFIG.SYS file. This file is located in the root directory of your hard drive. From a DOS prompt, C:, type the command edit config.sys. Once in the editor, either change the LASTDRIVE=line or add a LASTDRIVE statement greater than the amount of drive letters. For example the line could be: LASTDRIVE=Z. Make sure to save and exit.
What are the parameters I put in CMOS (BIOS setup) for my SCSI hard drive? SCSI host interface cards do drive translation for the computer and operating system. The computer's CMOS should be set to SCSI if it has this option, if not then set it to 'none' or 'not installed' for the specified hard disk drive. Follow the instructions that came with the SCSI host interface card for proper installation procedures.
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I have a PCI SCSI RAID controller and the drives go offline during heavy loads. Why? The most common reason for drives being marked offline is cabling/termination issues. Make sure the cabling is of the highest quality (twisted pair or Teflon ribbon) that's within SCSI specifications as to maximum bus length, impedance matching, and maximum allowed devices. For best results, use a system level SCSI terminator (LVD/SE) on the end of the cable, instead of using the last drive for termination. Make sure the hard drives are set to provide SCSI Termination Power, if supported. Rarely is drive firmware an issue—more often a SCSI controller BIOS or ASPI driver update.
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Can I boot my from my SCSI hard drive? The drive will need to be partitioned and formatted for your computer's operating system before it can be used as the boot drive. Follow the instructions in the operating system or computer manual for installing a new hard drive and loading the operating system. Most SCSI controllers feature on-board ROM BIOS to controll the disk drive. Older SCSI controllers may use jumpers or a start up disk to access BIOS. Enable SCSI BIOS for the "active" partition, C:, to be recognized. Using more than one SCSI controller? Choose only one to start up. Typically only one active partition is allowed each drive. If BIOS has support for removable disks as hard drives, choose: All Disks. Consult your SCSI controller or system guides.
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Can I boot from my SCSI hard drive with an IDE/EIDE drive installed? The system will use the IDE as bootable hard dive in most computer systems. Most new BIOS' have a SCSI Boot Sequence (option) setting. Some combo SCSI/IDE cards will allow the reverse or some add-in secondary IDE cards will allow the SCSI to boot first.
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Sustained data transfer rates for SCSI hard drives issue.
Many factors contribute to disk drive performance. One useful measure is data throughput rate or sustained transfer rate -provided other system components process the data as fast as the disk drive can either read or write the data. In general, higher data transfer rates from the disk to the SCSI controller lead to improved system performance. Data transfer rates are often quoted within the "Specifications" section of the product manuals. Yet it is important to realize that controller overhead, SCSI cable and termination issues, are major factors that affect sustained data transfer rates. If your sustained user data rates are lower than expected, this indicates a bottleneck in the system. A failing device, improper configuration, and termination issues are leading causes for poor performance. Be aware that transfer rates can be reduced, caused by several issues--poor quality cables, improper cable routing (causes signal reflection), SCSI Single Ended devices on an LVD SCSI bus, host limitations and more. It is commonly said that over 99% of poor performance issues are NOT drive related!
I have a SCSI RAID controller and the drives keep coming up marked dead/off-line. I can return the drives on-line again, but why is this happening and what can I do to fix it? There are many reasons why a SCSI controller or operating system marks one or more drives off line. It's important to make sure the cabling, termination, and drive enclosure hardware is suitable based on SCSI specification--or as required by your configuration. Use the best quality SCSI data cable. Make sure it is certified for either Ultra SCSI or Ultra 2 or Ultra 3(Ultra 160) or Ultra 320 SCSI. Most SCSI controller vendors support a line of cables and terminators for their product. If there is a mix of LVD (low voltage differential) and non-LVD devices on any one SCSI channel? Then Ultra SCSI (single-ended narrow) specifications apply--cables not longer than 1.5 meters, and not more than four devices supported. Not enough SCSI Termination Power can be at fault. As a precaution, be sure the last two physical devices (hard drives)on each SCSI channel, provide Term.
Power to the SCSI bus. For SCSI bus Termination Enable, we highly recommend you use either the disk array enclosure (if supported) or a system terminator at cable end. If you use LVD drives, you must use an LVD terminator. If you are using SCSI single ended devices, or mixing single-ended and LVD you must use an active terminator at cable end. Sometimes the disk array enclosure, the drive slide trays may be defective, or there could be a problem with the SCA back-plane logic board. Try the drive in a different system--does the failure follow to another 'known good' platform? The system power supply can be at fault. Under or over current will cause the drive to spin down in the name of data integrity. You will want to make sure a high quality power supply is used, and that it will meet the power needs of your system. Software drivers and BIOS on the SCSI RAID controller can affect timing and communications. You should visit all system component and operating system manufacturer's Web sites, to confirm that all drivers and firmware is up to date.
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Where to locate ASPI drivers for SCSI host adapters?
Locations (URL's) for various SCSI host adapters manufacturers:
Adaptec
www.adaptec.com/support/index.html
AdvanSys (Now ConnectCom Solutions)
www.connectcom.net
Advanced Storage Concepts (ASC)
www.advstor.com/
AMI
www.ami.com
(select quick link for MegaRAID drivers)
ATTO
www.attotech.com
(select: Support/ Downloads)
Diamond Multimedia (MM)
www.diamondlegacy.com/products/drivers/driver-index.htm
DPT (acquired by Adaptec, December 1999)
http://www.adaptec.com/worldwide/support/supportindex.html
ICP Vortex (acquired by Intel, March 2001)
www.icp-vortex.com
Initio
www.initio.com/
(select links for Support, then Software downloads)
Mylex (acquired by IBM, September 1999)
www.mylex.com/support/download/index.html
SIIG
www.siig.com
Symbios
www.lsilogic.com
Tekram
www.tekram.com/updatesmain.asp
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My SCSI hard drive doesn't spin up when I apply power to it. What's wrong? Some of the legacy SCSI hard drives must have a jumper in place to allow the drive to spin up when power is supplied. Check the jumper settings on the unit to make sure the spin up option (if supported) is properly enabled.
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If my hard drive only fails on the manufacturer’s SCSI diagnostic tests, does this mean that it is defective and should be returned? If your hard drive fails on the manufacturer’s SCSI diagnostic tests and provides you with a validation code, it is likely in this case, that your drive has a problem and should be replaced. There are other possible reasons for a test failure, for example a bad or improperly connected cable. If your drive fails the test, make a note of the failure and the validation code, then contact your hard drive’s manufacturer to determine if your drive should be replaced.
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Will SCSI performance suffer if I attach more than one drive to my controller? Using multiple hard drives with most PCI to SCSI host adapters is NOT a performance penalty --unless you're running a FILE SERVER. For a multi-user environment, choose either a dual channel SCSI host adapter or hardware RAID SCSI host adapter. Hardware RAID solutions offer an onboard CPU and extra memory for the SCSI host adapter. Most SCSI controllers do not support the SCSI command set feature of disconnect / reconnect (DT/DC) for hard drives. These SCSI controllers are seen as optimized for a power user. The 'power user' is defined as an individual using a workstation, with one hard drive and other standard SCSI peripherals such as CD recorders, scanners, or removable drives. Windows 95, 98, and Windows ME and Windows 2000, do not support the SCSI feature of disconnect /reconnect. None of these Operating Systems take advantage of disconnect / reconnect except for NT servers using RAID 0, 1 and performance RAID arrays using RAID level 5, and what's becoming known as RAID '10', combining the features of RAID 0 and 1.
Disconnect / reconnect can often be enabled in the BIOS of the SCSI host adapter when using multiple hard drives. With DT/DC enabled, the SCSI controller will disconnect from a hard drive after an input /output (I/O) operation, but will immediately reconnect to that same hard drive until the entire I/O request has been fulfilled. Without operating system support for DT/DC at the SCSI host adapter, having disconnect /reconnect enabled in the SCSI BIOS, can actually degrade performance in a workstation environment by adding overhead to the I/O process. Establishing and re-establishing the link to a particular device adds delay between bursts of data. With DT/DC disabled at the SCSI host adapter, optimum performance is achieved in a WORKSTATION when the I/O involves data transfer to / from a hard drive. With DT/DC disabled in SCSI host adapter, multiple hard drives in a multi-tasking SERVER environment will have a significant performance decrease.
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Potential problem with LVD termination and the Adaptec 2940U2/W.
There is a potential problem in configuring proper SCSI LVD drive termination with early release SCSI Ultra 2 (Adaptec AHA-2940U2W SCSI) host adapters. When both internal and external LVD drives are attached, you may see the card report "Host Adapter Configuration Error" at power on. Adaptec has identified that some early AHA-2940U2W SCSI host adapters are unable to correctly set termination when both internal and external LVD (Ultra 2) drives are attached to the controller. This issue is caused by either the SCSI host adapter or improper SCSI termination and is not a problem with the hard drive. According to Adaptec, if you receive this error message, disconnect either the internal or external cable from the AHA-2940U2W SCSI card. If the error message is eliminated you need to apply a BIOS patch to the SCSI host adapter. Please refer to the Adaptec Support web site for more information. Download file 2940U2UP.EXE that is available to resolve this problem. Carefully read the information and instructions provided by Adaptec on their Web site and in the readme.txt file for the patch.
Should I update the BIOS on my SCSI controller? And if so, how would I do this? If you are not having any problems with your system, it is not necessary to update the BIOS for your SCSI controller or host adapter. However, it is recommended that you always contact the manufacturer of your SCSI controller for any available BIOS updates. SCSI controllers (and drives) reach development end-of-life. New updates may not be available. Some SCSI controllers require OEM specific versions to work with the specific chipset on the controller. This is especially true if your SCSI controller or host adapter was installed by an OEM manufacturer (such as Compaq, HP, Dell). BIOS utilities are typically updated with a manufacturer provided utility. Before you proceed, identify your specific make, model of SCSI controller, the current BIOS revision numbers, and part number (typically printed on BIOS chip).
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SCSI Cable and Termination issues.
Cables are one of the most important considerations in Ultra SCSI systems. Ultra SCSI allows for a maximum total cable length of only 1.5 meters (all cables totaled). There should also be at least six inches between devices (ten inches is preferred and twelve is optimal), for proper communication. Add to this the fact that a large percentage of cables are out of tolerance concerning the SCSI specifications. This is further exacerbated by the use of both internal and external cables, which will frequently cause impedance mismatches. Our recommendation is to use quality twisted-pair or Teflon ribbon cables that are properly shielded if being used externally. Improper termination can cause many problems, especially with Ultra SCSI systems. The specifications call for termination to be supplied at the ends of the SCSI bus. Many people however, frequently terminate the last physical device on the cable, sometimes allowing unused cable to hang off the end of the SCSI chain. This is not the proper method, because excess cable beyond the terminated device, longer than 0.1 meter (about 3.5 inches), constitutes a stub, and must be terminated. Also, if both internal and external cables are used, with one SCSI host adapter, then the host adapter should not be terminated, and instead, termination should be located at only the ends of the cables attached.
Can I use a standard 68-pin ribbon cable with an Ultra2 SCSI installation? SCSI specifications about connectors, device spacing, cables and termination are very exact. Legacy cables differ from LVD cables in wire gauge and impedance specifications. Termination schemes may be passive, active, active negation, or differential. The ANSI SCSI specifications for SPI-3 (SCSI Parallel Interface-3) states: 'Balanced interconnect media e.g., twisted-flat, discrete wire twisted pairs, combined with matched printed circuit board traces should be used with LVD transceivers...[the] use of non-twisted flat cables causes cross-talk problems....". Using cables and termination incompatible with the devices or SCSI controller can show up as various failures. One example is using inexpensive, out-of-specification cables, to connect an external hard drive with internal LVD devices. Perhaps also daisy-chaining devices with cables of dubious quality, using inexpensive passive termination. Consult your system manufacturer for guidance with proper SCSI protocol. Problems from using inferior or dubious quality cables are: system bus hangs at device detection, no device detection, intermittent system operation, or data corruption.
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My SCSI hard drive runs hot - Ventilation guidelines for high speed SCSI disk drives.
The environment (rack, cabinet, or drawer) for the hard disk drive must provide cooling of the electronics and head/ disk assembly (HDA). Although the hard drive can be mounted in any orientation, when you install the drive, be sure to direct airflow that creates the least amount of airflow resistance, while providing airflow to the electronics and HDA. Airflow patterns are created by one or more fans either forcing or drawing air. Choose the shortest possible path between the air inlet and exit to minimize the travel length of air heated by the drive and other heat sources within the environment (rack, cabinet or drawer). Airflow velocity of approximately .6 meters /sec. (150 linear feet /min. for a 10,000 RPM drive) over the HDA is recommended.
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My SCSI hard drive will not boot. What's wrong? Check all cable connections, data and power. Test data cable by trying a known good cable or a known working drive. Check jumper settings. For SCSI make sure the last device on cable is terminated. Or use an active system level terminator. Check controller card by trying a known good card. For SCSI check the host adapter by trying a known good adapter card. Set the host to asynchronous negotiation and the slowest transfer rate available. Make the drive the only device in the system if it's not already. Make sure the Primary Partition is set "Active" in FDISK (option 2 at the main menu). In some cases a "NO ROM Basic" error message will be displayed during boot up if the Primary Partition is not set active. Boot from a floppy disk that contains the files: COMMAND.COM, IO.SYS, MSDOS.SYS, and FDISK.EXE. At the A:> prompt type "fdisk/mbr" (leave out the quotes) and press the ENTER key (this step refreshes the DOS Master Boot Record). Then type "sys c:" and press the ENTER key (this step transfers the operating system's startup files to the C: drive). Try drive in a known good system.
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How do I perform basic troubleshooting for a SCSI hard drive in an Apple Macintosh? The first step to returning a disk drive is clear confirmation that the drive is truly defective. Many disk drives we are asked to replace are not, in fact defective. It is in your best interest to perform some basic troubleshooting first. You will avoid the inconvenience, expense, and unnecessary effort of replacing a working drive. Often a faulty cable, or wrong jumper settings can be interpreted as a drive failure. Older Apple computers typically do not recognize any non-Apple branded component. This is so, as it is cost prohibitive to test every product in every Apple configuration. For Apple computer users with a generic (not Apple branded) hard drive, you must use any of several hard drive diagnostic utilities available on the market.
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Can I use Apple's Drive Setup to initialize and partition my new SCSI drive? The "Drive Setup" utility provided with Apple O/S versions prior to 8.6 are for Apple OEM hard drives, shipped by Apple in Macintosh/Power Macintosh computers. Apple O/S 8.6 and newer shipped with hard disk setup utility Version 1.7.3, this latest version is generically friendly, and will mount most non-Apple hard disks. The utility can also be downloaded from Apple's web site. For those of you running older Apple O/S and systems with non-Apple hard drives, Apple recommends that customers use third-party formatting utilities. Note: Apple computer is unable to test or support issues that may arise from using non-Apple branded hardware/software.
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Do I need CHS parameters (Cylinders, Heads, and Sectors) for my SCSI hard drive? SCSI parameters are not like ATA (IDE). Normally, a SCSI drive doesn't require any drive parameters as it is not configured in CMOS (system setup) the same as ATA drives. Logical drive geometry is created by the host adapter automatically. This data is based on the number of Logical Block Addresses (LBA) on the drive. Occasionally, an operating system may require a logical parameter to be entered into a definition file. Many current operating systems such as Linux and versions of Unix and Solaris are self-configuring.
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Excessive heat and high-speed SCSI hard drives issues.
Even though over 90% of SCSI errors can typically be traced to cable and termination concerns, many users may not be aware that excessive heat can also cause erratic system behavior and premature component failure. Excessive heat can come from several unusual sources inside a computer case. Today's high-speed (7200 RPM and greater) hard disk drives, CD-ROM "burners" (CD-R or CD-RW), PCI cards, and even SCSI bus terminators can generate enough heat to cause your system to become unstable and/or result in the premature failure of one or more system devices. Overheating can come from unexpected sources. Transferring large data files or uncompressed graphic files can generate significant heat. Reading or writing a white page (an all ones pattern on the SCSI bus) causes heat to be generated. CD-ROM "burners" often overheat when more than one CD is written at a time.
You will want to add an extra fan for the CD-R or CD-RW. It is very important to confirm that your computer system is qualified for using high-speed disk drives. Today's 7,200 to 10,000 RPM drives need 150 linear feet/min. of directed airflow. The long-term reliability of a hard drive is closely related to it's operational temperatures. Most high speed hard drives are designed for an operational temperature of about 30°C (86°F). Ambient case temperatures above 50°C (122°F) or below 5°C (41°F) can decrease drive reliability, performance, and product life.
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My SCSI hard drive runs slow during start up, running applications, or accessing data. What’s wrong? Many elements affect computer system performance: CPU clock rate, the amount of system RAM, graphics and video cards, and SCSI bus speed. Each component plays a role in the performance of the overall system, depending on the applications in use. The hard drive is only one element. To confirm the integrity of your SCSI hard drive, use the drive diagnostic program. This quick test will confirm overall drive integrity . If the test shows no trouble found, the problem remains elsewhere in the system. Apple Macintosh users should find third party applications available (at additional cost) from FWB, Tech Tool Pro and others. Macintosh supplied diagnostic utilities may (or not) function on a generic (not MAC branded) drive.
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Why is the hard disk drive NOT as fast as advertised? Advertised transfer rates are based on the fastest speed at which the drive can send data across the ribbon cable from the drive buffer. The transfer stops every time the buffer re-fills. This process continues until a command is complete. Data transfer rates differ as much as system configurations. The one thing that analysts have control of is the speed at which data transmits across the data ribbon cable from the drive's buffer.
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How do I make my SCSI hard drive a master or slave? SCSI does not use the concept of master or slave assignment, as in ATA (IDE) devices. The user is only concerned as to what SCSI ID number is assigned to a device, and which device(s) will terminate the SCSI bus. SCSI devices occupy (i.e. respond to) one address on the SCSI bus. The SCSI hard drive provides a means (jumpers or shunts) to select one of eight (ID 0-7) or sixteen (ID 0-15) available addresses. Each device on the SCSI bus is assigned a unique address. This address is used during bus arbitration and selection, or reselection of SCSI devices. The host adapter vendor or system manufacturer is the best resource for SCSI bus configuration questions.
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System hangs when using SCA-2 pin converter or interface adapter.
Many pin converters use an older style of termination - passive termination - to cancel the unused lines. This is a valid but now obsolete form of termination. An inherent difficulty with passive termination is maintaining stable terminator voltage. Fluctuations occur and reduce signal quality. If TP (terminator power) is set either too high or low, the terminated lines can be placed at too high or low of a reference point, causing problems with SCSI phase transitions. The single ended (SE) electrical class depends on very tight termination tolerances, but the passive 132 ohm termination defined in 1986 is mismatched with the cable impedance (typically below 100 ohms). Not a problem at low speeds with only a few devices connected, but signal reflections cause errors when transfer rates increase and/or more devices are added. In ANSI SCSI-2 protocols, an active terminator was defined that lowers termination to 110 ohms. This is a major boost to system integrity. Another problem with pin converters is that some use a single conductor grounding method. This method has all ground lines connected through a single conductor (legacy 25 pin Macintosh product).
This type of connector is an acceptable solution with SE devices, but can cause erratic bus behavior when an LVD (low voltage differential) device is used with an LVD host adapter. Current model hard drives operate in either SE or LVD mode. Hardware and firmware contained within the Quantum Atlas and Viking drives monitor pin 38 on the SCSI bus (DIFFSENS) to determine the correct mode of operation (SE or LVD) when attached to the SCSI bus. The drive's firmware then configures its SCSI interface circuitry to match the mode (SE or LVD) prevailing on the SCSI bus. When the DIFFSENS (differential sense capability) line is grounded, an LVD device will be forced to operate as a SE device. Additionally, when this line is grounded, the entire SCSI bus switches to SE mode. With some pin converters many of the ground lines are not even connected. This could cause a LVD device to stay in LVD mode, when it is actually attached to a Single Ended host, causing severe problems. Some pin converters do not offer all the options offered by the 12 additional SCA conductors, such as Delay Spin or Remote Start. This is a minor usability issue, but could still pose a problem.
Many pin converters on the market offer little, if any, shielding. You should use cables that are double-shielded (foil and braid). Make sure the connector hoods (or shrouds) are each connected to the shield braid. Noise can be introduced which degrades signal quality. Inferior or poor quality cables are usually the case of seemingly mysterious SCSI difficulties. Pin converters are not recommended for use with high performance systems that utilize either 68 or 50 pin SCSI interfaces. It is recommended that you return any SCA drives that you may have purchased for either Wide SCSI (68 pin) or Narrow SCSI (50 pin) drives. The best practice dictates that you match the pin out of your SCSI host adapter. Interface converters are not a single solution for all the problems you can encounter, but it is prudent to have properly matched equipment. If your situation dictates that you must use a pin converter, there are several vendors that do offer quality SCA to 50-pin or SCA to 68-pin pin converters. Instructions for configuring these adapters should be supplied by the adapter vendor. How do I properly terminate a LVD (Low Voltage Differential) SCSI hard drive? LVD SCSI hard drives do not provide on board termination, relying instead on "system-level termination".
This means an LVD/SE terminator must be used at the end of the cable to provide SCSI bus termination. An active single-ended (SE) terminator, or other SCSI device (eg; drive, scanner, CDROM) that provides SCSI Bus Termination Enable (TE), can be used, although this action forces the whole SCSI channel to run in single-ended mode. SCSI Ultra 160 and 320 controllers often use an auxiliary port for attaching legacy (50 pin and single ended) devices. A proper cable must be used for LVD operation. SCSI-3 specifications recommend "twisted pair" cable sets. Cables and active LVD/SE termination devices can be purchased from your SCSI controller manufacturer or system board vendor.
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How do I properly terminate a LVD (Low Voltage Differential) SCSI hard drive? LVD SCSI hard drives do not provide on board termination, relying instead on "system-level termination". This means an LVD/SE terminator must be used at the end of the cable to provide SCSI bus termination. An active single-ended (SE) terminator, or other SCSI device (eg; drive, scanner, CDROM) that provides SCSI Bus Termination Enable (TE), can be used, although this action forces the whole SCSI channel to run in single-ended mode. SCSI Ultra 160 and 320 controllers often use an auxiliary port for attaching legacy (50 pin and single ended) devices. A proper cable must be used for LVD operation. SCSI-3 specifications recommend "twisted pair" cable sets. Cables and active LVD/SE termination devices can be purchased from your SCSI controller manufacturer or system board vendor.
Power down the system, disconnect the main computer power (AC) cable and disconnect the drive's data cable. Use only one hard drive, SCSI controller and SCSI cable to isolate the issue. Confirm that the SCSI drive's Termination Power and Termination Enable functions are enabled. Confirm that the spin delay options (if any) are correctly set. When power is supplied, a "working" drive will spin up, perform its self-check, and then stay spun-up. A drive that spins up and then spins back down (without the SCSI data cable attached) should be checked for: correct jumper configuration, or possible drive failure. Power Management can be set on many levels. SCSI controllers, System-board BIOS, the operating system, or third party utilities can manipulate drive functionality. If the drive still spins down after this test, and after review of cables, connectors, SCSI bus termination, media scan, or a SCSI "low-level" format, are inconclusive, the drive may be defective.
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Can't partition a SCSI hard drive with FDISK. What happens? If you are experiencing difficulty creating a partition on a SCSI disk drive try these basic troubleshooting steps:
- Check all cable connections. Test data cable by trying a different cable or try the cable on a known working drive.
- Check the jumper settings.
- Check termination.
- Check the SCSI controller. Test it by trying a known good controller or a known working drive.
- Check SCSI controller default settings. Set the controller to asynchronous negotiation and the transfer rate to 10Mbs (or the slowest setting).
- Make this offending drive the only SCSI device in the system and re-test.
- Run a SCSI 'low level' format routine provided by the host adapter manufacture.
Try the drive in a different system.
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What is the SCA interface? The SCA interface was designed to provide a standard connection for systems using hot swappable drives. SCA interface drives connect to a SCSI back-plane that provides power, configuration settings such as SCSI ID, and termination of the SCSI bus.
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How can an SCA interface drive be attached to a standard 50-pin or 68-pin SCSI host adapter? An SCA adapter is necessary to attach an SCA interface drive to a standard SCSI host adapter. An SCA adapter should provide power and termination as well as jumper settings for SCSI ID and other drive features. Some drive models may offer configuration options on the drive. Please check the drive's configuration settings.
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