[CentOS] LVM thinpool snapshots broken in 6.5?

Dennis Jacobfeuerborn dennisml at conversis.de
Sat Jan 11 15:32:34 UTC 2014

On 09.01.2014 23:54, Dennis Jacobfeuerborn wrote:
> Hi,
> I just installed a CentOS 6.5 System with the intention of using thinly
> provisioned snapshots. I created the volume group, a thinpool and then a
> logical volume. All of that works fine but when I create a snapshot
> "mysnap" then the snapshot volume gets displayed in the "lvs" output
> with the correct information but apparently no device nodes are created
> under /dev/mapper/ or /dev/(volumge_group_name).
> Any ideas what might be going on here?

For the people who run into this as well:
This is apparently a feature and not a bug. Thin provisioning snapshots 
are no longer automatically activated and a "skip activation" flag is 
set during creation by default. One has to add the "-K" option to 
"lvchange -ay <snapshot-volume>" to have lvchange ignore this flag and 
activate the volume for real. "-k" can be used on lvcreate to not add 
this flag to the volume. See man lvchange/lvcreate for more details.
/etc/lvm/lvm.conf also contains a "auto_set_activation_skip" option now 
that controls this.

Apparently this was changed in 6.5 but the changes were not mentioned in 
the release notes.


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