Persistent Binding To Ensure Scsi Id Assignment - IBM TS3100 Setup, Operator, And Service Manual

Figure 18. Examples of SCSI element addressing
The SCSI specification does not allow gaps in the SCSI element addressing. Special handling is needed
for empty drive slots to fulfill the specification. Also temporarily removed drives need to have their
addresses that are preserved to not confuse the attached host and host application. Generally only drives
that are currently physically available or temporarily removed are reported. Empty (unused) slots that are
located at the bottom or the top must not be reported, with an exception in a 'removed' condition. A
drive slot that does not contain a drive, and has a position between used slots, must be reported as a
SCSI element. To signal the host application that this slot is not usable, its ACCESS bit is disabled.
Note: When the number of drives in your library are reduced, update the Logical Library configuration.
This action removes the Attention LED on the front panel and the exclamation mark on the Home screen
that indicates that a drive is missing.
Updating the Logical Library configuration also updates the drive element addressing and drive
numbering. Replacing LTO half height drives with full height drives might require you to execute Restore
Factory Defaults to correctly update the drive element addressing and drive numbering. See "Configure
Library: Save/Restore" on page 150.

Persistent binding to ensure SCSI ID assignment

When a server is booted, devices are discovered and assigned SCSI target and LUN IDs. It is possible for
these SCSI assignments to change between boots. Some operating systems do not guarantee that devices
are always allocated the same SCSI target ID after rebooting. Also, some software depends on this
association, so you do not want it to change. The issue of SCSI ID assignment is addressed by persistent
binding.
Persistent binding is an HBA function that allows a subset of discovered targets to be bound between a
server and device. Implemented by a worldwide node name (WWNN) or worldwide port name
(WWPN), persistent binding causes a tape drive's WWNN to be bound to a specific SCSI target ID. After
a configuration is set, it survives reboots and any hardware configuration changes because the
information is preserved. If a drive must be replaced, the new drive assumes the WWNN of the old drive
because the WWNN for the drive is location-dependent within the library. Because the WWNN does not
change, persistent binding does not need changing, thus preventing a potential outage.
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IBM TS3100 Tape Library and TS3200 Tape Library: Setup, Operator, and Service Guide Machine Type 3573
4U Unit with only FH drives
(1 logical library)
SCSI Element Slot
4
257
3
2
256
1
4U Unit with FH and HH drives
(1 logical library)
SCSI Element Slot
4
258
3
257
2
256 1