OT - Scalable email server solution needed
jan.grant at bristol.ac.uk
Sun Apr 9 17:14:32 UTC 2006
On Sun, 9 Apr 2006, Bill Moran wrote:
> I have only a small amount of experience with Cyrus. However:
> Based on that document, it appears as if you're dodging the bullet with
> backups. My interpretation is that Cyrus keeps mailboxes in some sort
> of db file. If a db file is being modified while you're backing it up,
> the backed up version will be inconsistent, thus the entire mailbox
Not quite. Cyrus maps the imap hierarchy onto directories, with one
(written once only) file per message. As flat-file as you can get. On
top of this are per-folder index files (which can be recreated using
reconstruct) holding stuff like preformatted IMAP responses, header
indexes etc. That's where cyrus gets its speed from.
Additionally there's a per-server "mailboxes" DB holding folder
information (including ACLs), per-user seen/subscription databases and a
deliverdb for duplicate suppression.
The latter can all be stored in multiple formats, including bdb; hot
backups for these work much the same way as for anything other bdb.
It's not perfect, but there's minimal bullet-dodging.
jan grant, ISYS, University of Bristol. http://www.bris.ac.uk/
Tel +44 (0)117 3317661 http://ioctl.org/jan/
ioctl(2): probably the coolest Unix system call in the world
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