[DRBD-user] data integrity in drbd

Lars Ellenberg lars.ellenberg at linbit.com
Fri Aug 26 14:28:31 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.

On Fri, Aug 26, 2011 at 05:50:59PM +0800, Lyre wrote:
> Hi all:
>     Is there a way to check the data integrity on both node? I've encounter
> an confusing problem.
> We have two drbd devices, 20Gb one for application, and 300Gb one for oracle
> database(oracle was installed in a different location, which were not
> replicated), csums-alg & verify-alg were configured to crc32c,  bandwidth
> was 100M.

I suggest to not use the same algorithm for csums-alg and verify-alg,
so the verify can detect differences which the csums based resnc thought
where identical due to identical checksums respective hash colision.

I further suggest that you use stronger hash algorithms for both.
Like md5 and sha1, or similar.

>  I try to upgrade our app & database on secondary(node2) , by disconnect and
> promote 2 drbd devices to primary and then perform the upgrade, it was fine.
> Then I try to roll back the seondary the original version, by  drbdadm --
> --discard-my-data connect drbdX.  After drbd sync,  oracle was unable to
> startup, it reports data corruption. So I issue drbdadm verify, but it
> doesn't report anything, everything seems good.
> I disconnect drbds and then mount them on both side, md5sum all files on the
> disk. I diff the output from both side and found that serval database file's
> md5 value wasn't identical. Then I connect drbds and found that it begin to
> sync about 30Gb's data. I didn't the device read only, but have all
> applications stopped.
> BTW,  In earier, I've try to recovery the underlying  lvm devices from
> snapshot, but get IO error, so I just canceled and resync it. Does it
> matter? Since I've get rid of drbd there.

Can you give more detail there?
What did you do?
Did that manipulate DRBD meta data as well?
Did you bypass DRBD at some point during the process?

: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
please don't Cc me, but send to list   --   I'm subscribed

More information about the drbd-user mailing list