HP StorageWorks Ultrium Full-Height SCSI Tape Drives User Guide (EH853-90905, August 2007)

Figure 27 SCSI termination in daisy-chained external drives

SCSI cables

Cables ma

tter 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 n ote below on SE and LVD interfaces.

• For best performance, keep leng ths to a minimum, but avoid very short overall leng ths (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

afteryourSCSIcables. Inparticular,takecarewhenconnectingordisconnectingnotto

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 Storag eWorks

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.

SCSI conﬁguration guide