cyrus imap slow on Fedora 13&14

[Bron Gondwana]

On Mon, Dec 27, 2010 at 07:37:16PM +0000, Andre Felipe Machado wrote:
> Hello,
> >From the docs, the default db backend is now skiplist for all those.
> Unfortunately, for some access profiles, it has not good performance, as our
> tests showed.

I'd be interested in seeing what's actually causing the slowdown, because
the use case given:

"The problem is when user read big mail boxes (e.g. 1000+ mail in one
folder) from webclient (Squirrelmail) installed on same or other server."

doesn't actually make very many DB queries, and is unlikely to be affected
by the database backend.  It's a long time since I used squirrelmail - but
I'd be interested in seeing telemetry logging from the session, which should
show the commands that are taking time.  Particularly if you could give a
telemetry log with the older version on a similar sized mailbox, so we could
see what squirrel is doing differently.

> You could try to change some of them to more suitable backends, for example,
> quotalegacy for quotas, berkeley-nosync for deliver.db, where better reliability
> is not critical (easy rebuild or restore from backups).
> The debian defaults has been demonstrated as good choices at our tests at our
> environment. But you should test at *your* environment.

Quotalegacy is IMHO the best for quotas - I don't know why it's "legacy",
no database contention between users for a very freqently changed value!

Bron.