Dovecot 2.2.16: disappearing messages, mismatched summaries, duplicated messages, excessive full re-downloads

[Timo Sirainen]

On 18 Apr 2015, at 15:02, David Gessel <gessel at blackrosetech.com> wrote:
> 
>>> dovecot.log shows runs of this error:
>>> Apr 15 09:02:37 imap(user at domain.com): Warning: Maildir /mail/domain.com/user//.Sent: Expunged message reappeared, giving a new UID (old uid=306286, file=1429102024.M826331P1156.host,S=1678,W=1724:2,S)
>>> 
>>> or this error:
>>> Apr 15 10:04:00 indexer-worker(user at domain.com): Warning: Maildir /mail/domain.com/user//.Sent: Expunged message reappeared, giving a new UID (old uid=306803, file=1428785463.M645546P27215.host,S=5389,W=5442:2,S)
> 
> One possibility is that there is a scrub/verify routine running that is checking the actual size vs. reported size of messages, and perhaps that routine doesn't know about ZFS compression:
> 
> zroot/ezjail                             used           117G      -
> zroot/ezjail                             compressratio  1.25x     -
> zroot/ezjail                             compression    lz4       local
> zroot/ezjail                             logicalused    137G      -
> 
> and is seeing something anomalous and trying to "fix" that, triggering a rescan.  A long shot and seems unlikely, but I have no other ideas.

No. My best guess is that (your) ZFS+FreeBSD is simply not behaving the way Dovecot wants filesystems to behave (readdir() sometimes skipping over files). I don't have any other suggestion than trying a different filesystem or OS. I haven't heard ZFS having these problems before though.