On 11/15/2010 10:36 AM, David Mayo wrote:
One day last week I noticed a performance dip on our IMAP server. We tracked the cause down to periodic "checkpointing" of the deliveries database by the LMTP daemon on our backend server. The only real effect on users is that deliveries don't happen for the duration of the checkpointing cycle, although on this occasion I noticed the IMAP server was running unusually slow during this period and I also discovered the MUPDATE server was unavailable shortly afterwards for creating new mailboxes. This is presumably because the MUPDATE server was busy in the backed-up delivery process. Having looked at the source code, we can see that ctl_cyrusdb does not touch deliver.db and it is not possible to force checkpoints on or off within lmtpd. Ideally we want to schedule the checkpointing to a "less sociable" time. On our setup, the checkpoint runs every couple of days and usually takes 4-6 minutes[1]. We run cyr_expire every night to remove entries older than 3 days from the duplicate deliveries database but this is the only maintenance we can schedule on this database.
No solution, but I wonder why your checkpoint takes so long? With similar DB size it take only seconds here.
Nov 8 21:18:04 student2 lmtpunix[6541]: skiplist: checkpointed /var/imap/deliver.db (650493 records, 67180160 bytes) in 5 seconds
Nov 12 23:14:06 student2 lmtpunix[26425]: skiplist: checkpointed /var/imap/deliver.db (768262 records, 80010936 bytes) in 11 seconds
Do other people suffer from this? Is there a patch that anyone has written and/or will be submitting upstream any time soon? We are running Cyrus 2.3.13 across a front end, a back end and a replication host for around 25,000 users. Regards, Dave. David Mayo Networks/Systems Administrator University of Bath Computing Services, UK [1] Nov 4 15:32:33 imap.bath.ac.uk lmtp[29595]: [ID 301543 mail.info] skiplist: checkpointed /opt/etc/imapd/deliver.db (787618 records, 74775536 bytes) in 386 seconds Nov 9 14:26:06 imap.bath.ac.uk lmtp[1676]: [ID 301543 mail.info] skiplist: checkpointed /opt/etc/imapd/deliver.db (386167 records, 36638408 bytes) in 232 seconds Nov 11 12:45:35 imap.bath.ac.uk lmtp[2497]: [ID 301543 mail.info] skiplist: checkpointed /opt/etc/imapd/deliver.db (657254 records, 62540568 bytes) in 396 seconds ---- Cyrus Home Page: http://www.cyrusimap.org/ List Archives/Info: http://lists.andrew.cmu.edu/pipermail/info-cyrus/
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