Public bug reported:
Binary package hint: linux-image
Happens on : 2.6.27-7-generic, 2.6.27-9-generic (x86_64)
Severity : Major issue for running a server using LVM snapshots.
Regression : This issue temporarily existed in a much older kernel version
(don't remember which, think it was a 2.6.1x) and was quickly fixed by the
time. Now it's back :-(
This problem definitely didn't exist in Hardy with its 2.6.24 kernels.
Description : On a system with LVM snapshots active, intensive I/O may
randomly (read: often) result in an I/O freeze on the snapshots origin
volumes, leading to a complete system lockup after a while. I/O to the
snapshots themselves is unaffected.
Probably some kernel race condition while writing to snapshots origin
and COWing to snapshots.
Typical situation : Active server with backups being performed from LVM
snapshots. The running backup goes on unaffected from the snapshots, but
after a while all other running processes on the system start freezing
in I/O wait mode when they request disk access (to the snapshots origin
volumes).
- Once backup is finished, trying to deactivate LVM snapshots freezes as
well.
- System cannot be cleanly rebooted or halted. As I/O is blocked this
results in a necessary brutal hard reboot.
** Affects: linux-ports-meta (Ubuntu)
Importance: Undecided
Status: New
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[Intrepid kernel 2.6.27] LVM snapshots causes I/O freeze and system lock / hang
https://bugs.launchpad.net/bugs/303064
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