> On 11/05/2021 01:07 Marcin Gryszkalis <m...@fork.pl> wrote: > > > Hi > I have exim/dovecot server that worked great for last few years and two > weeks ago it got ill ;) > First were users reporting errors on saving mails to Sent (timeouts). > Now the logs are infested with warnings about long waits: > > May 10 10:18: Maildir /mail/xxx Synchronization took 193 seconds (1 new > msgs, 0 flag change attempts, 0 expunge attempts) > May 10 10:18: Maildir /mail/xxx Synchronization took 125 seconds (1 new > msgs, 0 flag change attempts, 0 expunge attempts) > May 10 10:18: Maildir /mail/xxx Synchronization took 211 seconds (1 new > msgs, 0 flag change attempts, 0 expunge attempts) > May 10 10:18: Maildir /mail/xxx Synchronization took 107 seconds (8 new > msgs, 0 flag change attempts, 0 expunge attempts) > May 10 10:18: Transaction log file /mail/xxx was locked for 36 seconds > (Mailbox was synchronized) > May 10 10:18: Transaction log file /mail/xxx was locked for 160 seconds > (Mailbox was synchronized) > May 10 10:18: Transaction log file /mail/xxx was locked for 72 seconds > (Mailbox was synchronized) > May 10 10:18: Locking transaction log file /mail/xxx took 60 seconds > (syncing) > May 10 10:18: Locking transaction log file /mail/xxx took 38 seconds > (syncing) > May 10 10:18: Locking transaction log file /mail/xxx took 35 seconds > (syncing) > > It looks like i/o risen from 150writes/s to 500writes/s (in top hours) - > but there's no real change in number of emails or the volume. Number of > users is steady (~100 active users, ~250 imap sessions), number of > emails (by count or by volume) is rising and falling within 15% margin. > > The box is FreeBSD 11.4, dovecot is 2.3.13. > Filesystem is ZFS, disks are fine, free space is around 20% (~200GB) > Layout is Maildir. CPU is not overloaded (2x6core), same with memory (48GB). > > I didn't change anything in configuration. > > Tonight I did some finetuning like maildir_copy_with_hardlinks=yes or > mail_fsync=never/optimized (I'm not happy with that but I'm afraid it > won't really help and I'll be able to revert that). I'm also thinking > about switching from Maildir to sdbox (I know it won't hurt). > > I don't know where to look to find where the i/o goes. I don't have any > metrics/stats enabled (I looked at the docs but it looks it's not really > simple and needs some digging to get valuable config). Maybe somebody > has suggestions what to look for? > > For detailed per-process stats I need to rebuild kernel with dtrace > (other night I guess)... Simple top (in i/o mode - similar to linux's > iotop) doesn't catch short living processes (like LDA deliveries). > > best regards > -- > Marcin Gryszkalis, PGP 0xA5DBEEC7 http://fork.pl/gpg.txt
One thing that does come to mind is that you are delivering outside dovecot. Without knowing your system better, I would suggest that one thing to try would be to use dovecot-lda to deliver mail. Are your users directly accessing the maildir? Aki
