[DRBD-user] data integrity in drbd

Lyre 4179e1 at gmail.com
Sat Aug 27 06:08:16 CEST 2011

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Thanks Arnold

What's the correct to rcovery a drbd snapshot?

I believe the volume-before-resync was snapshot of the underlying
logic volume , not the /dev/drdrbX, during recovery, I should dump the
snapshot to logic volume, is that right?

The traditional lvm snapshot recovery was dd the snapshot to a file,
the dd the file to the original volume. However, in my environment, I
don't have enough space. Would lvm merge help? However it doesn't
supported by SLES yet.

In my situation, what should I do to completely resync the data of
secondary node, including the drbd metadata ?

On Sat, Aug 27, 2011 at 1:27 AM, Arnold Krille <arnold at arnoldarts.de> wrote:
> On Friday 26 August 2011 17:33:09 Lyre wrote:
> > Yesterday,  On the secondary,  I shut down drbd, try to use rsync to
> > recovery the snapshot, but failed. Then I start drbd to resync from the
> > primary node. It was the only time I bypass drbd, howerver,the application
> > seems good at that time.
> >
> > This afternoon, we continue our experiment, disconnect drbd on secondary,
> > changed something and resync from priamry.  Oracle was unable to start.
> > drbd status suggest that both node were uptodate, drbadm verify doesn't
> > report any error. Disconnect one side and mount drbd device on both node,
> > md5sum show that some files were different.
> rsync works on file(-system)-level, drbd compares disks and blocks. So by
> mixing both these tools, even though the filesystem mounted by hand on both
> seems to be the same, the disks aren't the same anymore once rsync did write
> something.
> And during the time drbd is off and you changed something, drbd will not
> recognize these changes. Due to the fact that a) drbd was off at that time and
> b) drbd works on block-device-level.
> If this sounds like "you are fu**ed", that is partly intended. Mixing the
> levels of access is experimental at best and you better have a backup before
> starting such stuff.
> Have fun,
> Arnold
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