dovecot - Jan 2011 - Storing Dovecot index files on sql

We have been communicating with the mailling list on another thread
regarding dotlocking on the dovcot-uidlist over an NFS share, and I was
hoping to get some ideas on whether or not a sql database would be a
suitable location for storing the dovecot index files. Our though process
so far has been that storing the index files on NFS with the maildir has
not worked very effectively when we are using multiple Dovecot servers
(even using sticky IPs in our load balancer), and using local storage is
not possible with a cluster of machines, so we got to thinking about what
type of storage platform would be suitable for these index files that would
provide native locking of the data while multiple servers accessed and
wrote to it. Our question to the community is whether sql storage for index
files has ever been considered, what issues would this introduce, and if
it's even feasible? 

Thanks everyone! 

Michael

On 2011-01-27 1:49 PM, list at airstreamcomm.net wrote:
> Our though process so far has been that storing the index files on
> NFS with the maildir has not worked very effectively when we are
> using multiple Dovecot servers
As has already been pointed out, this is precisely what Timo wrote the
dovecot Director for.

-- 

Best regards,

Charles

On Thu, 2011-01-27 at 12:49 -0600, list at airstreamcomm.net
wrote:
> Our question to the community is whether sql storage for index
> files has ever been considered, what issues would this introduce, and
> if it's even feasible? 
Its performance would be horrible.

Only dovecot.index.cache file's contents would in theory benefit in
being stored in a bit more complex database, but the database would have
to have very low latency. Maybe Berkeley DB would work ok. Any SQL
database would have too high latency. dovecot.index and
dovecot.index.log files' contents are something that don't really fit
into database at all.

I'll still probably implement support for SQL databases at some point,
but I'm not expecting the performance to be anything close to mailbox
formats on filesystem.