|Summary:||Potential for deadlock when snapshots are taken of mirrors|
|Product:||Red Hat Enterprise Linux 6||Reporter:||Jonathan Earl Brassow <jbrassow>|
|Component:||lvm2||Assignee:||Jonathan Earl Brassow <jbrassow>|
|Status:||CLOSED ERRATA||QA Contact:||Corey Marthaler <cmarthal>|
|Version:||6.0||CC:||agk, coughlan, dwysocha, heinzm, iannis, jbrassow, prajnoha, prockai|
|Fixed In Version:||Doc Type:||Known Issue|
Known Issue: Due to the limitations of the LVM 'mirror' segment type, it is possible to encounter a deadlock situation when snapshots are created of mirrors. The deadlock can occur if snapshot changes (e.g. creation, resizing or removing) happen at the same time as a mirror device failure. In this case, the mirror blocks I/O until LVM can respond to the failure, but the snapshot is holding the LVM lock while trying to read the mirror. If the user wishes to use mirroring and take snapshots of those mirrors, then it is recommended to use the 'raid1' segment type for the mirrored logical volume instead. This can be done by adding the additional arguments '--type raid1' to the command that creates the mirrored logical volume, as follows: ~> lvcreate --type raid1 -m 1 -L 1G -n my_mirror my_vg
|Last Closed:||2013-02-21 08:07:35 UTC||Type:||---|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
|Bug Depends On:||563924|
Comment 8 Jonathan Earl Brassow 2012-10-15 17:11:01 UTC
This bug will never be completely fixed WRT the 'mirror' segment type and snapshots. However, 'raid1' can be used in place of 'mirror' and does not suffer from this issue. Thus, this becomes a documentation and awareness issue. I am marking this bug as MODIFIED, although that is not technically correct. I don't want to CLOSE the bug without the release note stating that users should use the alternative. It could be argued that LVM should warn users if snapshots are attempted on 'mirror's and suggest 'raid1' instead...
Comment 12 Peter Rajnoha 2012-10-19 11:46:12 UTC
Doc only bug, this should appear as a "Known Issue" item in the 6.4 documentation.
Comment 16 errata-xmlrpc 2013-02-21 08:07:35 UTC
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. http://rhn.redhat.com/errata/RHBA-2013-0501.html