Dell PowerVault TL4000 - Manual (Page 269)

Appendix D. Enabling LUN Support in Linux
To verify the detection of a tape drive, administrators should check for its entry in
/proc/scsi/scsi
. Current versions of Linux may not scan the logical storage unit
(LUN) ID of every device. This can result in some TL2000/TL4000 devices not
being identified or listed in the /proc/scsi/scsi output. Administrators can follow
these steps to enable support for such devices.
1.
Type cat /proc/scsi/scsi. The output will look similar to the following:
Attached devices:
Host: scsi0 Channel: 00 Id: 01 Lun: 00
Vendor: IBM Model: ULT3580-HH3 Rev: 88M3
Type: Sequential-Access ANSI SCSI revision: 03
2. Identify the host adapter, channel number, target ID number, and LUN number
for the first LUN of the device to be configured. In this example, the IBM
Model ULT3580 (a drive in the TL2000/TL4000) is shown at the address, or
nexus, 0 0 0 0 — which means host adapter 0, channel number 0, ID 1, and
LUN 0. The TL2000/TL4000 always has the tape drive at LUN 0 and the robot
at LUN 1.
3. For each LUN that needs to be discovered by Linux, issue the following
command: echo "scsi-add-single-device H C I L">/proc/scsi/scsi H C I L
refers to the nexus described in step 2. So, with the TL2000/TL4000 robot
configured at LUN 1, type: echo "scsi-add-single-device 0 0 1
0">/proc/scsi/scsi
. The echo command will force a scan of each device at the
given nexus.
4. Type cat /proc/scsi/scsi again to verify that all devices are now listed. The
output will look similar to the following:
Attached devices:
Host: scsi0 Channel: 00 Id: 01 Lun: 00
Vendor: IBM Model: ULT3580-HH3 Rev: 88M3
Type: Sequential-Access ANSI SCSI revision: 03
Attached devices:
Host: scsi0 Channel: 00 Id: 02 Lun: 01
Vendor: IBM Model: 3573-TL Rev: 7.10
Type: Medium Changer ANSI SCSI revision: 05
Administrators should add the echo command to the Linux boot scripts
because the device information is not persistent and must be created each time
the system boots up. One example file that can be used for storing the
commands is /etc/rc.local. Note that configuring additional devices on a server
or a storage area network (SAN) can cause the devices to be reordered, which
requires administrators to modify the commands. If the Fibre Channel adapter
supports Persistent Bindings or an equivalent function, it can be enabled to
reduce the chance of devices being reordered upon discovery.
Note: This procedure must be run each time the server is booted. Also, if
backup application services are running (for example, they automatically
start when the OS loads), they must be disabled and re-enabled after the
above procedure.
The other way to enable LUN support is to recompile the kernel and enable
LUN scanning in the Adaptec driver, but it requires advanced knowledge of
Linux and will not be covered here. However, it will allow the server to always
boot and see the device without any manual procedures.
D-1