"splitlvcopy" - the usage - makes it sense

[ogniemi]

I was going to split LV copies (1 of 3) before backuping data from the LV being heavy loaded but I found in redbook it is not such clever.

"Note:
Although the splitlvcopy command can split logical volumes that are open,
including logical volumes containing mounted file systems, this is not
recommended. You may lose consistency between LogicalVolume and
NewLogicalVolume if the logical volume is accessed by multiple processes
simultaneously. When splitting an open logical volume, you implicitly accept
the risk of potential data loss and data corruption associated with this
action. To avoid the potential corruption window, close logical volumes
before splitting, and unmount file systems before splitting
"

If it is not possible, in which case (what for) the command may be usefull?

Has anyone experience with the tool?



thx,
M.

 

[bi]

I suppose if you want to take a backup of a filesystem and you don't want any activity going on in the filesystem while the backup is being taken, it would take a lot shorter amount of time to stop activity in the filesystem, unmount it, split the LV, then remount the filesystem than it would to actually do the backup. Users would be able to get back into the filesystem more quickly.

 

[ogniemi]

Additinal question:

Is it possible to join back splitted LV with the rest of LV copies? (making new LV opcy with "mklvcopy" there will be 100% stale partitions on this copy and synchroniozation process will take long time.)

regards,M.

 

[trifo]

Well, it makes no sense to "join back the lv". After you made a backup of the split copy of the lv, you will have to drop it and create a new 3. lv copy. Of course, it will be 100% stale, and will take time to recreate the healthy mirror. But this process will be done "on the fly" while users and processes can access the lv.

Maybe there is some solution to join back the lv copy and have only a few stale pp-s, but I do no know, how-to.

--Trifo