Dell TL4000 User Guide - Page 259

Appendix D. Enabling LUN support in Linux To verify the detection of a tape drive, administrators check for its entry in /proc/scsi/scsi. Current versions of Linux might not scan the logical storage unit (LUN) ID of every device. This results 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 looks similar to: 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 must 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 forces a scan of each device at the specific nexus. 4. Type cat /proc/scsi/scsi again to verify that all devices are now listed. The output looks similar to: 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 must add the echo command to the Linux boot scripts because the device information is not persistent and must be created each time that the system boots up. One example file that is used for storing the commands is /etc/rc.local. Configuring more devices on a server or a storage area network (SAN) might 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 is enabled to reduce the chance of devices that are reordered upon discovery. Note: This procedure must be run each time that 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 procedure. Another 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 is not covered here. However, it allows the server to always boot and see the device without any manual procedures. © Copyright IBM Corp. 2007, 2013 D-1