[DRBD-user] data integrity in drbd

Lyre 4179e1 at gmail.com
Fri Aug 26 11:50:59 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.

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 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.
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