LVM bitmap

[Gary Orban]

We have an HP Nclass Server that has JBOD disks that are doubly mirrored. As part of our normal procedures we split off one mirror for backup purposes and merge back when complete.

We ran into a scenario where when we did the merge , it took a verrrrry long time leaving me to believe it was doing a full merge.

Problem is the system wasn't rebooted. My question is , if we deactivate the VG's does the bitmap go away ???

[James R. Ferguson]

Hi:

If I understand your question, I believe that the answer is "no". According to the man pages, when "...using lvmerge, the bit map is used to decide which areas of the logical volumes need to be resynchronized. This bit map continues to exist until the merge is completed, or one of the logical volumes is extended or reduced, or the system is rebooted.".

From the man pages for 'vgchange': "...When the optional MirrorDisk/UX software is running, and a volume group is activated, LVM performs the necessary mirror consistency recovery for each logical volume in the volume group based on the state of the Mirror Write Cache and Mirror Consistency Recovery...".

Synchronization time is dependent on system load, the I/O configuration and the number of stale extents.

Regards!

...JRF...

[Gary Orban]

Have recreated in my test environment and later verifed with HP that the bitmap does indeed get destroyed when the VG gets deactivated.