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 : : LINBIT Information Technologies GmbH Tel +43-1-8178292-0 : : Vivenotgasse 48, A-1120 Vienna/Europe Fax +43-1-8178292-82 : __ please don't Cc me, but send to list -- I'm subscribed