HP StoreEver Ultrium Tape Drives - Manual (Page 74)

Figure 26 SCSI termination in daisy-chained external drives
SCSI cables
Cables matter in SCSI systems. There are two factors to consider: cable length and cable quality.
Cable length
• For LVD SCSI the maximum length for a single device is 25 meters. For multiple devices, the
maximum combined internal/external length is 12 meters.
• If you have a combination of LVD and SE devices on the bus, the maximum cable length reverts to
the SE specification. This is 3 meters for four or fewer devices, and 1.5 meters for more than
four devices. See also note below on SE and LVD interfaces.
• 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.
• Look after your 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.
With internal devices
HP StorageWorks Ultrium tape drives have a 68-pin wide, high-density SCSI connector. A suitable
cable with the correct termination is supplied with the tape drive. If you are using an HP StorageWorks
Ultrium drive on an internal bus with other peripherals that run at Ultra2 speeds, it is important that a
68-pin LVD-compatible ribbon cable is used. Do not connect your tape drive to lower-rated SCSI or
to narrow SCSI.
74 SCSI configuration guide