Deliverdb in a memcached

[Øyvind Kolbu]

On 2011-08-23 at 14:01, Ram wrote:
> On a very busy Imap server , duplicate suppression sometimes becomes the 
> bottleneck
> I have seen that If I disable duplicate suppression , my lmtp deliveries 
> are speeded up.
> 
> Duplicate suppression is important , but the database need not persist 
> for very long.
> I have seen in most of the cases if there is a duplicate mail ( due to 
> forwards , groups etc ), it arrives within 10 minutes of the first mail
> ( Any exception to this is too minor and can be ignored )
> 
> 
> IMHO There should be a configuration that the deliverdb can be, 
> optionally,  stored in memcached or directly in memory.
> Of course there are cons .. like loss of data on restart etc. But these 
> are OK.

A number of cyrus' databases are volatile and can be placed on tmpfs.
memcached seems overkill, and as of cyrus version 2.4.8 there are options
to specify the location of most databases, and thus be able to point some
of the to a tmpfs based directory.

We currently use the following:

mboxname_lockpath: /uio/PKG/tmpfs/lock
proc_path: /uio/PKG/tmpfs/proc
duplicate_db_path: /uio/PKG/tmpfs/deliver.db
statuscache_db_path: /uio/PKG/tmpfs/statuscache.db
tlscache_db_path: /uio/PKG/tmpfs/tls_sessions.db

and it reduces IO on the storage a lot.

-- 
Øyvind Kolbu
Postmaster
Universitetet i Oslo
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