[Dovecot] Dovecot and SATA Backend

[alex handle]

>
> Extra question, what is the better : iSCSI SATA backend or NFS share ?
> NFS share is more convenient to have a failover server.

Everyone wants to use nfs for mailstorage, because it is convenient,
but nfs is the wrong storage model for mail.
NFS shines on big files but metadata performance is low, too much overhead!

We currently have a mailcluster with 10000 mailboxes and the data ist
stored on a netapp storage.
If you have a Mailbox with more then 1000 mails, it gets slow over nfs.

Our new architecuture will look like this:

No NFS, no iSCSI we use DAS.
There will be multiple dedicated mailbox server in pairs with a small
postfix instance and dovecot.
These Servers will only be used for delivering/IMAP/POP3.
To get HA we use DRBD und Heartbeat in active/passive setup.
In the front there will be a IMAP/POP3 proxy to direct the user to his
mailbox server.

This setup scales and is cheap, you only have to find a way to
distribute the mailboxes around all mailbox servers.

I think rackspace email uses a similar setup with drbd and dovecot.