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HP StorageWorks Ultrium SCSI Tape Drives - HP Ultrium SCSI Configuration

Full-height SCSI tape drives

Ultrium 215/230

HP Surestore Ultrium drives are Ultra 2 Wide SCSI devices designed to operate on a low voltage differential (LVD) SCSI interface.

The drives support a burst transfer rate of 80 MB/sec and sustained transfer rate of 30 MB/sec (assuming 2:1 compression). To benefit from this level of performance, it is important to ensure that the drives are connected to a SCSI bus of a similar or higher specification. Hence the following are needed:

  • An Ultra 2 Wide, Ultra 160 or Ultra 3 SCSI host bus adapter. Ultra 2 Wide SCSI supports the maximum bus speed of 80 MB per second, Ultra 160 and Ultra 3 SCSI exceed this.

  • LVD-rated SCSI cabling and terminators. The LVD interface enables the data to be transferred at the drive's maximum rate and provides a maximum cable length of 12 meters.

If the SCSI bus does not meet the above specification, the performance of the drives can be restricted and it could take longer to back up the data. For example, HP Surestore Ultrium tape drives will function on Ultra Wide SCSI buses, but this is not recommended because the maximum bus speed drops to 40 MB/sec and maximum cable length may be restricted to three meters. (See note on SE and LVD interfaces.)

For optimum performance, it is recommended that the tape drive is connected to a dedicated host bus adapter. If multiple devices need to be connected to the bus, performance will not be restricted as long as no more than two devices are connected and they are of the same type (Ultra 2 Wide SCSI). Make sure that the last device on the SCSI bus is terminated. Do not attach the tape drive to the same SCSI bus as the disk drive.

See the section on "SCSI Termination" for more information about terminating HP StorageWorks Ultrium tape drives .

Ultrium 232/448/460

HP Surestore Ultrium 232, 448 and 460 drives are Ultra 3 Wide SCSI devices designed to operate on a low voltage differential (LVD) SCSI interface.

The drives support a burst transfer rate of 160 MB/sec and sustained transfer rates of 32, 48 and 60 MB/sec respectively (assuming 2:1 compression). To benefit from this level of performance, it is important to ensure that the drives are connected to a SCSI bus of a similar or higher specification. Hence the following are needed:

  • An Ultra 160 or Ultra 320 SCSI host bus adapter. Ultra 160 SCSI supports the maximum bus speed of 160 MB per second, Ultra 320 SCSI exceeds this. Note that Ultra 2 wide with a max bus speed of 80 MB per second is likely to be sufficient with typical data which compresses at around 2:1. If the data is likely to exceed 3:1 compression ratio then this HBA is likely to be the bottleneck.

  • LVD-rated SCSI cabling and terminators. The LVD interface enables the data to be transferred at the drive's maximum rate and provides a maximum cable length of 12 meters.

If the SCSI bus does not meet the above specification, the performance of the drives can be restricted and it could take longer to back up the data. For example, HP Surestore Ultrium tape drives will function on Ultra Wide SCSI buses, but this is not recommended because the maximum bus speed drops to 40 MB/sec and maximum cable length may be restricted to three meters. (See note on SE and LVD interfaces.)

For optimum performance, it is recommended that the tape drive is connected to a dedicated host bus adapter. If multiple devices need to be connected to the bus, performance will not be restricted as long the bus speed is sufficient. I.e. two devices requiring 60 MB/sec each (2:1 data) will operate unrestricted on an Ultra 160 HBA. Make sure that all the devices on the bus support the highest bus rate or they will limit the bus bandwidth available for all the other devices on that bus. Make sure that the last device on the SCSI bus is terminated. Do not attach the tape drive to the same SCSI bus as the disk drive.

See the section on "SCSI Termination" for more information about terminating HP StorageWorks Ultrium tape drives .

Ultrium 1840/960

HP StorageWorks Ultrium 1840 and 960 tape drives are high performance Ultra320 SCSI compatible devices; HP StorageWorks Ultrium 460 tape drives are high performance Ultra160 SCSI compatible devices.

The drives are designed to operate on a low voltage differential (LVD) SCSI interface and are not compatible with high voltage differential (HVD) SCSI devices.

Ultrium 1840 and 960 tape drives support a burst transfer rate of 320 MB/sec; Ultrium 460 tape drives support a burst transfer rate of 160 MB/sec.

To benefit from this level of performance, it is important to ensure that the drives are connected to a SCSI bus of a similar or higher specification. Hence the following are needed:

  • An Ultra320 bus for HP Ultrium 1840 and 960 tape drives. An Ultra160 or Ultra320 bus for HP Ultrium 460 tape drives.

    If the drive is attached to a lower specification SCSI bus, it will still work but data may not be transferred as quickly. Ultra2 SCSI is also supported, but performance may be degraded.

  • LVD-rated SCSI cabling and terminators. The LVD interface enables the data to be transferred at the drive’s maximum rate and provides a maximum cable length of 12 meters.

See the section on "SCSI Termination" for more information about terminating HP StorageWorks Ultrium tape drives .

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Half-height SCSI tape drives

Ultrium 1760/920

HP StorageWorks Ultrium 1760 and 920 tape drives are high performance Ultra320 SCSI compatible devices; HP StorageWorks Ultrium 448 and 232 tape drives are high performance Ultra160 SCSI compatible devices.

The drives are designed to operate on a low voltage differential (LVD) SCSI interface and are not compatible with high voltage differential (HVD) SCSI devices.

Ultrium 1760 and 920 tape drives support a burst transfer rate of 320 MB/sec; Ultrium 448 and 232 tape drives support a burst transfer rate of 160 MB/sec.

To benefit from this level of performance, it is important to ensure that the drives are connected to a SCSI bus of a similar or higher specification. Hence the following are needed:

  • An Ultra320 bus for HP Ultrium 1760 and 920 tape drives. An Ultra160 or Ultra320 bus for HP Ultrium 448 and 232 tape drives.

    If the drive is attached to a lower specification SCSI bus, it will still work but data may not be transferred as quickly. Ultra2 SCSI is also supported, but performance may be degraded.

  • LVD-rated SCSI cabling and terminators. The LVD interface enables the data to be transferred at the drive’s maximum rate and provides a maximum cable length of 12 meters.

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What is SCSI?

The Small Computer Systems Interface (SCSI) is popular because it offers a fast and flexible method of connecting a variety of devices to a host computer. The SCSI standards define both the physical connections between the devices (cables and connectors) and the protocols devices use to communicate with each other.

The standards

There have been three general standards:

  • SCSI-1, which is now obsolete.

  • SCSI-2, which is very common, and still a current standard.

  • SCSI-3, which is an emerging set of linked standards that define much more than the simple bus systems used by the earlier versions. SCSI-3 transports includes Fibre Channel, Wide Parallel SCSI (single-ended and Low Voltage Differential : LVD or LVDS),, FireWire (IEEE 1398), Low Voltage Differential (LVD or LVDS), and Fast Serial Attached SCSI (SAS). Some of these standards are now being used on PC platforms.

Another variant is ATAPI, which uses an EIDE physical bus to pass SCSI protocols to connected devices. Technically, this is not part of the SCSI-3 standards, although some operating systems (notably Windows NT) manage ATAPI devices as if they were fully SCSI.

SCSI is a backward-compatible standard, so that SCSI-2 and SCSI-3 devices can almost always be made to work together.

SCSI is a bus interface, all the devices are connected to a single cable (some of this may be inside and some outside the host computer's case). The connection to the host itself is known as the Host Bus Adapter (HBA). A single computer can have several HBAs, each with its own SCSI bus, this is a common arrangement in high-performance servers. Some host bus adapters (such as the Adaptec 3940 W) have more than one SCSI bus available on a single card.

Various terms are used when describing SCSI devices. These terms relate to the factors that affect performance and cable length:

  • The speed of the data bus, which may be Fast, Ultra, Ultra 2, Ultra 3, Ultra 160, or Ultra 320.

  • The width of the data bus, which may be Narrow or Wide.

  • The voltage level of the interface, which may be single-ended (SE) or low voltage differential (LVD).

As described above, HP Surestore Ultrium drives are all Ultra 2 (or better) wide SCSI devices designed to operate on a low voltage differential SCSI interface.

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Setting up the SCSI bus

Each device on a SCSI bus, including the SCSI host bus adapter (HBA), must be configured with a unique ID (identifier). The SCSI bus must be terminated.

NOTE: HP recommends that a dedicated host bus adapter is used for the tape drive. A suitable adapter is available from HP as an accessory (see "Ordering Information").

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SCSI ID numbers

For wide SCSI buses, the SCSI ID will be a number from 0 through 15, so a typical wide SCSI HBA can accommodate up to fifteen other devices. (On narrow SCSI buses, the SCSI ID is a number from 0 through 7.)

SCSI IDs are usually set on the device itself (sometimes via configuration software) and must have a unique SCSI ID, but some newer devices are capable of selecting an unused ID automatically when powered-up (these are known as "SCAM" devices). HP StorageWorks drives are SCAM-1 compliant. This means that the drive will return its SCSI ID to the host bus adapter in response to a SCSI inquiry, but it will not allow the adapter to change the SCSI ID.

The drive can be assigned any unused ID between 0 and 15. Do not use SCSI ID 7, which is reserved for the SCSI controller. SCSI ID 0 is typically assigned to the boot disk and should also not be used unless the tape drive is on a dedicated SCSI bus.

SCSI ID 7 is normally reserved for the HBA because it has the highest priority on the bus. On wide buses, the priority runs from 7 (highest) to 0, then 15 down to 8 (lowest).

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Identifying SCSI IDs

If the computer already has devices connected to the SCSI bus, it is important to know their IDs to avoid any conflict with the new tape drive. Here are some methods of finding out the information:

  • The fastest and easiest way is to run HP Library & Tape Tools. HP Library and Tape Tools will check the SCSI configuration, including the SCSI controller itself and any devices currently attached to it. Click here to download or to find out more information about HP Library and Tape Tools .

  • Most computers display a list of SCSI devices and IDs during the boot-up process. This usually scrolls past very fast. Press the PAUSE key, to halt the scrolling and view the list.

  • On a Windows NT installation, select SCSI Adapters from the Control Panel, select a device in the Devices tab and click Properties to view information about the device, including its SCSI ID.

  • If a Novell NetWare is installed, use its LIST DEVICES command.

If none of these is available, try the following sources of information:

  • The details of all installed devices and settings may have been written down and stored with the computer's documentation (for new computers, this is often done by the supplier).

  • The HBA's documentation should tell which settings to be used.

  • Look at each device to find out its ID. This is usually easy with external devices. With internal devices, use the help of the device's documentation to identify the SCSI ID setting, which is usually set with jumpers.

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Setting the SCSI ID on HP StorageWorks Ultrium drives

Internal HP StorageWorks drives

On internal HP StorageWorks drives, set the SCSI ID by attaching or removing jumpers at the rear of the drive.

Figure 1: SCSI ID Jumpers and Example Settings for an Internal Drive

External HP StorageWorks drives

On external HP StorageWorks drives, the ID is displayed on the rear panel and can be set by pressing the little buttons above and below the number.

Figure 2: SCSI ID Setting on External Drive

Removable HP StorageWorks drives

On removable HP StorageWorks drives, the ID is set on the back of the tape array.

Figure 3: SCSI ID Setting for a Tape Array 5500

Figure 4: SCSI ID Setting for a Tape Array 5300

For all cases, see the Getting Started Guide that came with the tape drive for more details. Note that host adapters check SCSI IDs only at power-on, so any changes will not take effect until the host system is power-cycled.

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SCSI termination

Terminators are essential, as they provide the correct voltages on the SCSI bus and prevent unwanted signal reflections from interfering with data transfers. The rule is:

There must be termination at both physical ends of the bus and only at the ends.

There are two main types of termination, active and passive. Active terminators reduce interference and allow faster data throughput. On devices with high transfer speeds, such as HP StorageWorks Ultrium drives, active termination is required. Multi-mode active terminators are used with ultra-2 wide LVD SCSI buses.

Normally the HBA forms one end of the SCSI bus and provides termination. Therefore, make sure that the other end of the bus is terminated.

Internal drives

HP StorageWorks Ultrium internal tape drives do not provide termination. Usually the internal SCSI cable in a server has a number of SCSI connectors along its length and a terminator at the end farthest from the host bus adapter. These will usually be a small, rectangular block of plastic attached to the cable end and marked "SCSI Terminator."

Figure 5: Termination of Internal Drive

1 - SCSI Cable (Correctly Terminated)
2 - Tape Drive
3 - SCSI Controller Connection
4 - Power Cable
5 - Power Supply

As long as this terminator is attached, no further action needs to be taken. However, if other devices are attached to the cable, make sure that they have termination removed or disabled.

NOTE: If you have an internal and external device attached to the same SCSI bus, the HBA will be in the middle of the cable and thus its termination must be disabled. See the host bus adapter's documentation for details of how to do this.

External drives

For HP StorageWorks Ultrium external tape drives the enclosure provides active termination.

As long as the drive is the only device on the SCSI chain, no terminators are required. The green ACT Term LED on the rear of the drive indicates whether auto-termination is active (on) or not (off).

Figure 6: Termination with One External Device

If there are more than one device on the SCSI bus, daisy-chain them by connecting an LVD-rated cable from the SCSI-OUT connector on the first device to the SCSI-IN connector on the second device. Assuming two Ultrium tape drives are connected, the enclosure on the second drive provides termination. The green ACT Term LED on the rear of the first drive will be off while on the rear of the second drive it will be on. If the second device is not an Ultrium external drive, make sure that it is terminated using an LVD-rated multimode terminator.

Figure 7: Termination with Multiple Devices

Removable drives

For HP StorageWorks Ultrium removable tape drives, termination is provided by connecting a terminator to the spare SCSI connector on the rear of the tape array. There are two connectors for each bay in the tape array. It doesn't matter which is used for SCSI-IN and SCSI-OUT.

If the removable drive in the tape array is attached to a separate bus, then, for each bay in use, attach a terminator to the spare connector for each device.

If the removable drives are used to mirror backups, daisy-chain the devices (but no more than two on each SCSI bus). Connect an LVD-rated cable from the spare SCSI connector for the first device to one of the SCSI connectors for the second device and attach the terminator to the spare SCSI connector for the second device.

Refer to the tape array documentation for detailed instructions.

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SCSI cables

Cables matter in SCSI systems. There are two factors to consider:

  • Cable length: For LVD SCSI the maximum length for a single device is 12 meters. For multiple devices, the maximum combined internal/external length is 12 meters. For best performance, keep lengths to a minimum, but avoid very short overall lengths (less than 0.5 meters).

  • Cable quality: It is important to use good quality cables. Generally speaking, cable quality affects performance and reliability. This is particularly true for external, shielded cables.

For HP StorageWorks Ultrium internal drives, you need a SCSI ribbon cable with the correct termination. The drives have a 68-pin wide, high-density SCSI connector. If an HP StorageWorks Ultrium drive is used on an internal bus with other peripherals that run at Ultra 2 speeds, it is important that a 68-pin LVD-compatible ribbon cable is used.

The cable provided with HP StorageWorks Ultrium external tape drives will attach to a computer with a wide LVDS SCSI connector (68 pins). If the server or host bus adapter is equipped with a very high density (VHD) wide SCSI connector, a 68-pin HD-to-VHD converter or 68-pin HD-to-VHD cable will need to be ordered. See Ordering Information.

For HP StorageWorks Ultrium removable tape drives, appropriate cables are provided with the tape array.

Look after the SCSI cables. In particular, take care when connecting or disconnecting not to damage the high-density connectors. Avoid putting excessive twists in external shielded cables, as this can cause premature failure.

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Note on SE and LVD interfaces

SE and LVD define how the signals are transmitted along the cable.

  • With single-ended (SE) SCSI, each signal travels over a single wire and each signal's value is determined by comparing the signal to a paired ground wire. Signal quality tends to decrease over longer cable lengths or at increased signal speed.

  • With low voltage differential (LVD) signaling, signals travel along two wires and the difference in voltage between the wire pairs determines the signal value. This enables faster data rates and longer cabling with less susceptibility to noise than SE signaling and reduced power consumption.

If LVD SCSI devices are used on the same bus as single-ended devices this will switch the LVD SCSI host adapter into single-ended mode and restrict both cable length and bus speed.

If only LVD SCSI devices are connected, the bus will operate in low voltage differential mode and Ultra 2 speeds will be enabled. A combination of Ultra and Ultra 2 devices can be used. Each device will operate at its optimum speed.

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