[Dovecot] (1.0.13) fsync failed: Disk quota exceeded for some accounts

[Eric Marin]

Hello all,

We've recently migrated the mail server used by our 5000 students, from 
Tru64/UW-IMAP/Procmail/Postfix/mbox to Debian Etch/Dovecot/Deliver/Postfix/Maildir

E-mails are not stored directly on the server (except for index and control files), but on an NAS 
that exports the students' homedirs on NFS. Each student has a 100MB quota on the NAS.

Here is the configuration :
vega:~# dovecot -n
# 1.0.13: /etc/dovecot/dovecot.conf
log_timestamp: %Y-%m-%d %H:%M:%S
protocols: imap pop3
listen: [::]
ssl_disable: yes
disable_plaintext_auth: no
verbose_ssl: yes
login_dir: /var/run/dovecot/login
login_executable(default): /usr/lib/dovecot/imap-login
login_executable(imap): /usr/lib/dovecot/imap-login
login_executable(pop3): /usr/lib/dovecot/pop3-login
login_greeting_capability(default): yes
login_greeting_capability(imap): yes
login_greeting_capability(pop3): no
login_process_size: 32
login_max_processes_count: 1024
mail_privileged_group: mail
mail_location: maildir:~/Maildir:INDEX=/var/mail/index/%u:CONTROL=/var/mail/control/%u
maildir_copy_with_hardlinks: yes
maildir_copy_preserve_filename: yes
mail_executable(default): /usr/lib/dovecot/imap
mail_executable(imap): /usr/lib/dovecot/imap
mail_executable(pop3): /usr/lib/dovecot/pop3
mail_plugin_dir(default): /usr/lib/dovecot/modules/imap
mail_plugin_dir(imap): /usr/lib/dovecot/modules/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/modules/pop3
pop3_uidl_format(default):
pop3_uidl_format(imap):
pop3_uidl_format(pop3): %08Xu%08Xv
namespace:
   type: private
   separator: /
   inbox: yes
namespace:
   type: private
   separator: /
   prefix: mail/
   hidden: yes
auth default:
   cache_size: 1024
   passdb:
     driver: pam
     args: blocking=yes cache_key=%u dovecot
   userdb:
     driver: passwd
     args: blocking=yes



When one mails a student that has filled his quota, one immediately receives this message :
"Your message to <studentx> was automatically rejected:
Not enough disk space

Reporting-UA: vega; Dovecot Mail Delivery Agent
Final-Recipient: rfc822; studentx
Original-Message-ID: <490F0A9A.8030109 at utc.fr>
Disposition: automatic-action/MDN-sent-automatically; deleted"

And in /var/log/mail.log :
(...) save failed to INBOX: Not enough disk space
(...) Rejected: Not enough disk space


So far, so good, except that for *some* users (and I can't seem to find anything unusual about their 
account), one gets this in /var/log/mail.log :
Nov  6 10:42:24 vega deliver(studentx): 
fsync(/voletu/users/studentx/Maildir/tmp/1225964544.P25878Q0M80993.vega) failed: Disk quota exceeded
Nov  6 10:42:24 vega deliver(studentx): msgid=<2254E7BC-665D-4599-B719-825E3A58DC1D at utc.fr>: save 
failed to INBOX: Internal error occurred. Refer to server log for more information. [2008-11-06 
10:42:24]
Nov  6 10:42:24 vega postfix/local[25827]: 010F45EC18: to=<studentx at vega.utc.fr>, 
orig_to=<studentx at etu.utc.fr>, relay=local, delay=0.2, delays=0.02/0/0/0.17, dsn=4.3.0, 
status=deferred (temporary failure)

So for *some* users, it seems that Deliver doesn't detect that there isn't enough space, it tries to 
write the e-mail and of course fails, then reports an error, and Postfix interprets this as a 
temporary error and retries later.

After about a week :
vega:~# qshape deferred
                                          T  5 10 20 40 80 160 320 640 1280 1280+
                                  TOTAL 500  1  4  3  9 12   6   8  17  140   300
                             etu.utc.fr 499  1  4  3  9 12   6   8  17  139   300
                            vega.utc.fr   1  0  0  0  0  0   0   0   0    1     0



For the students that have this problem (about 30 for now), this happens *even* if I delete 
~studentx/Maildir, /var/mail/index/studentx and /var/mail/control/studentx, let Deliver recreate the 
necessary files (by sending the user a mail) so that everything is clean, artificially fill the 
quota with a big file in the homedir, then send a mail again. It gets deferred...


I have looked at the changelog for Dovecot, but have not found a clear clue that is a bug (if it is 
!) that has already been corrected in a more recent version...
Though if possible, I'd like to keep the Debian package (from etch-backports) instead of compiling 
it from source.

Also, while I've found Dovecot's wiki to be surprisingly informative, there are still a few points 
that did not seem very clear :
- should I use the quota:fs plugin in this case (it seems to work out well without it for most users) ?
- would it work in v1.0.13 on NFS ?
- if it worked, and I enabled it, what would change for me ?
- what is *supposed* to happen without the quota plugin when a user has filled his quota : mail is 
rejected, or mail is deferred ?
- and what about imap_quota ?


Best regards,
Eric