[Dovecot] Performance of Maildir vs sdbox/mdbox

[Mark Moseley]

On Wed, Jan 18, 2012 at 8:39 PM, Stan Hoeppner <stan at hardwarefreak.com> wrote:
> On 1/18/2012 7:54 AM, Timo Sirainen wrote:
>> On Wed, 2012-01-18 at 20:44 +0800, Lee Standen wrote:
>
>>> * All mail storage presented via NFS over 10Gbps Ethernet (Jumbo Frames)
>>>
>>> * Postfix will feed new email to Dovecot via LMTP
>>>
>>> * Dovecot servers have been split based on their role
>>>
>>>   - Dovecot LDA Servers (running LMTP protocol)
>>>
>>>   - Dovecot POP/IMAP servers (running POP/IMAP protocols)
>>
>> You're going to run into NFS caching troubles with the above split
>> setup. I don't recommend it. You will see error messages about index
>> corruption with it, and with dbox it can cause metadata loss.
>> http://wiki2.dovecot.org/NFS http://wiki2.dovecot.org/Director
>
> Would it be possible to fix this NFS mdbox index corruption issue in
> this split scenario by using a dual namespace and disabling indexing on
> the INBOX?  The goal being no index file collisions between LDA and imap
> processes.  Maybe something like:
>
> namespace {
>  separator = /
>  prefix = "#mbox/"
>  location = mbox:~/mail:INBOX=/var/mail/%u:INDEX=MEMORY
>  inbox = yes
>  hidden = yes
>  list = no
> }
> namespace {
>  separator = /
>  prefix =
>  location = mdbox:~/mdbox
> }
>
> Client access to new mail might be a little slower, but if it eliminates
> the index corruption issue and allows the split architecture, it may be
> a viable option.
>
> --
> Stan

It could be that I botched my test up somehow, but when I tested
something similar yesterday (pointing the index at another location on
the LDA), it didn't work. I was sending from the LDA server and
confirmed that the messages made it to storage/m.# but without the
real indexes being updated. When I checked the mailbox via IMAP, it
never seemed to register that there was a message there, so I'm
guessing that dovecot never looks at the storage files but just relies
on the indexes to be correct. That sound right, Timo?