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.

Regards, Dennis