Dell PowerVault TL4000 - Manual (Page 48)

SCSI Element Addressing
Every logical library starts at the first drive slot with the current assigned element
start address (default value 256). It will be incremented from the bottom to the top
slots for every drive slot. There is one exception to this addressing scheme to
accommodate libraries currently in the field. A 4U library containing only full
height drives will continue to have the addresses assignments 256 and 257, thus
causing no interruptions to their operation. Drive slots will still be incremented by
1 for each drive slot position.
Note: Exchanging drives with different form factors will result in the library
needing to be reconfigured.
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 preserved to not confuse
the attached host and host application. Generally only drives which are currently
physically available or temporarily removed are reported. Empty (unused) slots
located at the bottom or the top should not be reported, with an exception in case
of a “removed” condition. A drive slot which does not contain a drive, and has a
position between used slots, needs to be reported as a SCSI element. To signal the
host application that this slot is not usable, its ACCESS bit will be disabled.
Note: When reducing the number of drives in your library, update the Logical
Library configuration. This will remove the Attention LED on the front
panel and the exclamation mark on the Home screen indicating that a drive
is missing.
Updating the Logical Library configuration will also update the drive element
addressing and drive numbering. Replacing LTO half height drives with full height
drives may require you to execute Restore Factory Defaults to correctly update the
drive element addressing and drive numbering. See “Configure Library:
Save/Restore Configuration” on page 5-57.
SCSI Element Slot
4
3
2
1
SCSI Element Slot
4
3
2
1
257
256
257
256
258
4U Unit with only FH drives
(1 logical library)
4U Unit with FH and HH drives
(1 logical library)
a77ug
16
5
Figure 3-5. Examples of SCSI element addressing
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