Red Hat Bugzilla – Bug 456447
udev vol_id probe of passive/unreadable devices causes slow bootup
Last modified: 2011-01-13 17:59:25 EST
Description of problem: udev takes a very long time (~20 minutes) to start on
systems connected to an active/passive SAN with many LUNs. It appears to be
taking a long time on running vol_id on the passive paths. Running this command
on one LUN takes between 2-3 minutes
[root@prod-xen2 ~]# time /lib/udev/vol_id --export /dev/sdc
There is an upstream patch designed to correct this:
Version-Release number of selected component (if applicable):
Looking at the logs you can see it try over and over
Jul 23 12:11:31 prod-xen2 kernel: end_request: I/O error, dev sdc, sector 0
Jul 23 12:11:31 prod-xen2 kernel: Buffer I/O error on device sdc, logical block 0
Jul 23 12:11:34 prod-xen2 kernel: end_request: I/O error, dev sdc, sector 0
Jul 23 12:11:37 prod-xen2 kernel: end_request: I/O error, dev sdc, sector 0
Jul 23 12:11:37 prod-xen2 kernel: printk: 1 messages suppressed.
Jul 23 12:11:37 prod-xen2 kernel: Buffer I/O error on device sdc, logical block 0
Backporting the above patch to current udev-095-14.16 and running vol_id is much
[root@prod-xen2 ~]# time ./vol_id --export /dev/sdc
and only probes the device once:
Jul 23 14:20:31 prod-xen2 kernel: end_request: I/O error, dev sdc, sector 0
Jul 23 14:20:31 prod-xen2 kernel: Buffer I/O error on device sdc, logical block 0
Created attachment 312503 [details]
vol_id patch for udev-095-14.16
This request was evaluated by Red Hat Product Management for
inclusion, but this component is not scheduled to be updated in
the current Red Hat Enterprise Linux release. If you would like
this request to be reviewed for the next minor release, ask your
support representative to set the next rhel-x.y flag to "?".
Apple computer requested this patch for Oracle Enterprise Linux as they
are seeing these delays with Sun storage using rdac multipathing.
please, what hardware can be used to test with?
hmm, you might try with a blank cd-rw in a cdrom
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
Previously, the udev helper application 'vol_id' ran several times if a device was unreadable. This caused a massive delay for the bootup process on some machines. With this update, 'vol_id' checks whether a device is readable only once and no longer causes a delay.
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.