Richard Elling wrote:
On Oct 12, 2009, at 2:12 AM, tak ar wrote:
I'm not aware of email services using sync regularly.
In my experience
with large
email services, the response time of the disks used
for database and
indexes is
the critical factor (for > 600 messages/sec
delivered, caches don't
matter :-)
Performance of the disks for the mail messages
themselves is not as
critical.
I'm not using database. I'm using qmail only. Sync don't matter?
I've not implemented qmail, but it appears to be just an MTA.
These do store-and-forward, so it is unlikely that they need to
use sync calls. It will create a lot of files, but that is usually
done async.
I can't speak for qmail which I've never used, but MTA's should sync
data to disk before acknowledging receipt, to ensure that in the event
of unexpected outage, no messages are lost. (Some of the MTA testing
standards do permit message duplication on unexpected MTA outage, but
never any loss, or at least didn't 10 years ago when I was working in
this area.) An MTA is basically a transactional database, and (if
properly written), the requirements on the underlying storage will be
quite similar.
--
Andrew
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