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 real 1m58.681s user 0m0.000s sys 0m0.003s There is an upstream patch designed to correct this: http://git.kernel.org/?p=linux/hotplug/udev.git;a=commitdiff;h=73ff769c90307e9ef2947c7ba013626fb65c1478 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 better: [root@prod-xen2 ~]# time ./vol_id --export /dev/sdc real 0m3.138s user 0m0.000s sys 0m0.001s 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. New Contents: 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. http://rhn.redhat.com/errata/RHBA-2011-0073.html