[linux-lvm] Continue an interrupted mirror sync?

[Stuart Gathman]

On 09/27/2013 05:26 AM, Justin Lee wrote:
> Hello,
>
> I would like to know If a mirror sync process is interrupted by some
> uncontrollable reason, is it possible to continue the sync process
> near the point where it was interrupted?
>
> Volume mirroring may take a long time to be done, if the connection of
> the storage device is over an unreliable channel (such as SAN, iSCSI
> or Fibre Channel) it is possible that ongoing sync will be interrupted
> over and over again due to frequent connection loss so that the sync
> will never complete...
>
> Has LVM existing solutions for the issue? Or any suggestion? Thank you!
Pretty much the entire purpose of the mirror log is to accomplish this 
(track which blocks are in sync).  Is this a real problem you've 
encountered (mirror log is broken), or a theoretical one?  If you 
created a mirror without a log, then yes, it pretty much has to start 
over each time.  A compromise might be to keep the log in memory.  This 
would handle SAN storage going up and down, but would have to start over 
after a reboot.