[Dovecot] Maildir Synchronization warnings

[Timo Sirainen]

On 5.8.2013, at 20.22, /dev/rob0 <rob0 at gmx.co.uk> wrote:

>> To improve performance you can remove these two since you're using
>> director. Also you could set maildir_very_dirty_syncs=yes.
> 
> What about mail_fsync=always and mmap_disable=yes? These are needed 
> for non-director NFS, but what about with director?

I'm not sure if mail_fsync=always is strictly required, but I don't think it's going to give you any performance improvements in any case. With mail_fsync=always the file is flushed to NFS storage in the fsync() call, while with mail_fsync=never the file is flushed to NFS storage in close() call. In both cases it's going to be flushed, but in error cases it's more confusing to see close() fail.

mmap_disable=yes isn't required, but if the NFS storage dies the processes start dying with SIGBUS instead of logging "read() failed: Input/output error". I'm not entirely sure how changing it affects performance. Could be worse or could be better. If someone finds our let me know. :)