Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Mon, Jul 21, 2008 at 09:53:09AM -0700, Jeffrey Froman wrote:
> Hello,
>
> > what are the sorts of things that might be causing
> > blocks to become out-of-sync on this resource?
>
> A bit of follow-up: verification errors have been hitting us this week
> with increased frequency. We are using Protocol C for replication of
> a 135GB resource, and the secondary device reports no disk errors of
> any kind.
>
> Yet verification continues to fail -- now up to about 3 times per week
> (checked daily). We now feel rather unconfident that we can switch
> roles on the two nodes reliably at any time, since we have no idea
> when or why synchronization is breaking.
>
> Is it possible that we are experiencing a race condition between
> verification and replication, and that the blocks which verification
> finds out-of-sync have actually just been updated by normal
> replication between nodes during the checksum comparison?
anything is possible.
though there should not be any race condition.
you are using 8.2.6, aren't you?
which file system?
> If so, is there any option that will force retries of failed checksum
> comparisons for each block that is compared during verification?
no.
did you try to compare the reported blocks "by hand"?
like
on both# dd if=/dev/whatever iflags=direct bs=512 \
skip=$reported_sector_number count=$reported_sector_count \
of=tmp.$HOSTNAME.$rsn.$rsc
then
on left# scp right:tmp.right.$rsn.$rsc .
# diff -U0 <(xxd tmp.left.$rsn.$rsc) <(xxd tmp.right.$rsn.$rsc)
> Is there anything else I can add to my configuration to help determine
> exactly when these blocks are falling out-of-sync?
do you use tcp checksum offloading?
any other tcp offloading?
did you try to enable "data-integrity-alg"?
(go for crc32c, should be good enough)
--
: Lars Ellenberg http://www.linbit.com :
: DRBD/HA support and consulting sales at linbit.com :
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