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A SCSI configuration guide
In this appendix:
• "SCSI in Ultrium devices" on page 43
• "SCSI terminology" on page 43
• "Setting up the SCSI bus" on page 44
• "Identifying SCSI IDs" on page 44
• "Setting the SCSI ID on HP StorageWorks Ultrium drives" on page 45
• "SCSI termination" on page 45
• "SCSI cables" on page 48
SCSI in LTO devices
LTO-4 and LTO-3 tape drives are high performance Ultra320 SCSI compatible devices; LTO-2 tape drives are high performance
Ultra160 SCSI compatible devices.
They are designed to operate on a low voltage differential (LVDS) SCSI interface and are not compatible with high voltage
differential (HVD) SCSI devices.
LTO-4 and LTO-3 tape drives support a burst transfer rate of 320 MB/sec; LTO-2 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. This means that you need:
• An Ultra320 bus for LTO-4 and LTO-3 tape drives. An Ultra160 or Ultra320 bus for LTO-2 tape drives.
If you attach the drive to a lower specification SCSI bus, it will still work but data transfer may not be as quick. Ultra2
SCSI is also supported, but performance may be degraded.
• LVDS-rated SCSI cabling and terminators. The LVDS interface enables the data to be transferred at the drive's maximum
rate and provides a maximum cable length of 12 meters.
Daisy chaining devices
NOTE:
We do not recommend daisy chaining the LTO-4 or LTO-3 tape drive with other devices.
If you need to connect multiple devices to the bus, performance may be restricted if there are too many devices on the bus
that are accessed simultaneously. Connecting devices of lower SCSI specification, such as Ultra2 or Ultra SCSI, may also
restrict performance to your tape drive. Using Single Ended 8-Bit SCSI devices on the same bus is not recommended, as
performance will be severely impacted and complicated bus configuration is required to overcome bus termination issues.
Make sure that the last device on the SCSI bus is terminated. We recommend that you do not attach the tape drive to the
same SCSI bus as the disk drive. See "SCSI termination" on page 45 for more information about terminating LTO tape drives.
SCSI terminology
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). You can have several HBAs in
a single computer, each with its own SCSI bus: this is a common arrangement in high-performance servers. Some host bus
adapters have more than one SCSI bus available on a single card.
StorageTek LTO Half-Height SCSI Tape Drive
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