External Drives; Why Is The Scsi Bus Type Important; Supported Scsi Bus Types - StorageTek LTO User Manual

External drives

A 68-pin, wide, VHDCI-to-HD68 SCSI cable is required to attach the tape drive to the host server. See also "Installing an
external tape drive" on page 23.

Why is the SCSI bus type important?

The SCSI bus type determines the speed at which data can be transferred between devices on the bus and the maximum
length of cable that can be used. LTO-4 and LTO-3 drives support a burst transfer rate of 320 MB/sec. LTO-2 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 drives. An Ultra160 or Ultra320 SCSI bus for LTO-2 drives. If you attach the
drive to a lower specification SCSI bus, it may still work but will transfer data at a lower speed.
• LVDS-rated SCSI cabling and terminators. The LVDS interface enables the data to be transferred at the drive's maximum
rate.
Table 2 Supported SCSI bus types
SCSI Bus Type
Ultra320 LVDS
Ultra160 LVDS
Ultra2 LVDS
Ultra wide LVDS
and single-ended
Ultra narrow,
single-ended
High Voltage Dif-
ferential
Supported
Yes. This is a recommended configuration for all LTO tape drives.
Do not daisy chain LTO–4 or LTO–3 tape drives because performance may be degraded.
Do not daisy chain LTO-2 tape drives with Ultra320 devices.
Yes. This is a recommended configuration for LTO-2 tape drives. It is an acceptable
configuration for LTO–4 and LTO–3 tape drives, but it could limit performance on the
LTO–4 tape drive.
Up to two LTO-2 tape drives may be daisy-chained. Do not daisy-chain LTO–4 or LTO–3
tape drives.
Yes. This is acceptable for one LTO-2 drive per bus.
Do not use with LTO–4 or LTO–3 tape drives and do not daisy-chain LTO-2 tape drives.
These are not recommended configurations because they will restrict performance.
No. This will severely restrict performance and you would need a suitable cable or ad-
apter.
No. The drive will not work and you may damage the drive or controller.
StorageTek LTO Half-Height SCSI Tape Drive 11