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Tuesday, June 23, 2015

RHEL 6.6, non IBM devices and UDEV rules

Few days back we had to move one of our TSM servers and its library - which is a shared one. Did it before with TSM version 5.x and everything was fine that day. Now we are on the 7.1 and I have found that even the SANDISCOVERY found the new path correctly (and updated it on the Library Manager), drives were not working.
TSM 6.x+ server does not run under "root" account anymore, but when the new device is discovered, its device file is created as RW for root only.
Normaly (when you manually add the new device) you update the device files privileges and create the links using "/opt/tivoli/tsm/devices/bin/autoconf -a", but this does not work automatically.

On the TSM Symposium 2013 in Berlin there was a great presentation "Tape configuration for TSM" by Bruno Friess which (among other things) solves this situation by using persistent names via "udev".
It only has a 2 minor limitations
a) Linux variant mentioned is SLES
b) lacks details for Linux, udev and non-IBM devices

As our Linux servers run on RHEL amd our libraries are Overland brand with HP tape drives, I had to modify the steps a bit:
a) udevadm info .... does not display serial numbers for HP tape drives and Overland libraries - you need sg3_utils package for having "sginfo" command to get the device serial numbers
b) links are created as /dev/library1 and /dev/drive1 (2, 3) pointing to corresponding /dev/sgX device with crw-rw-rw permissions
c) file below was created as /etc/udev/rules.d/71-persistent-tape.rules
# This file shoud create persistent devices for HP tapes and libraries used by TSM

# Known serial numbers
# <library1>    LIBRSN1234
# <drive1>      DRV1SN3456
# <drive2>      DRV2SN4567
# <drive3>      DRV3SN5678

KERNEL=="sg*", SUBSYSTEM=="scsi_generic", SYSFS{type}=="8", PROGRAM="/usr/bin/sginfo -s /dev/%k", RESULT=="*LIBRSN1234*", SYMLINK+="library1",MODE="0666"
KERNEL=="sg*", SUBSYSTEM=="scsi_generic", PROGRAM="/usr/bin/sginfo -s /dev/%k", RESULT=="*DRV1SN3456*", SYMLINK+="drive1",MODE="0666"
KERNEL=="sg*", SUBSYSTEM=="scsi_generic", PROGRAM="/usr/bin/sginfo -s /dev/%k", RESULT=="*DRV2SN4567*", SYMLINK+="drive2",MODE="0666"
KERNEL=="sg*", SUBSYSTEM=="scsi_generic", PROGRAM="/usr/bin/sginfo -s /dev/%k", RESULT=="*DRV3SN5678*", SYMLINK+="drive3",MODE="0666"
Many thanks to Bruno and hope this helps someone.

1 comment:

  1. I need to setup persistent binding on some VTL drives we defined recently. In AIX is it straight forward ? I haven't done it in years so totally forgot the process.