On Thu, Jan 13, 2011 at 07:36:12AM +0200, Jaques Cochet wrote: > > I'm working on a mail system design for an ISP that includes hosting > of multiple virtual domains managed by this ISP (300.000 mailbox). HA > and performance are both important concerns for the client, so I have > at least 2 of every server (webmail, pop3, imap, relay and smtp > (postfix)) for which i'm using either L4 or MX record load > balancing/HA.
I'm running a very similar service... > I hate the idea of distributing mailboxes among servers and I'm trying > to go for a single mailstore that is accessible by POP3/IMAP servers > and delivery SMTP servers and I'm planning to use a SAN for this. The > basic idea is to share the mailstore between SMTP servers (clustered > storage using GFS maybe) and make the same mailstore available to > POP/IMAP server using NFS. Am I on the right track here? We have incoming SMTP servers in front, that process/route messages, and deliver the messages that we're supposed to keep to postfix on the backend POP/IMAP servers for delivery to mailboxes. i.e. frontend MX and smarthosts have no access to the mailboxes, they just route the messages. The POP/IMAP servers are SAN attached, and we have a cluster filesystem (IBM GPFS) where all mailboxes are stored. This works well, but we're starting to grow out of it -- and need to do something soon. It's very comfortable to have everything spread over all spindles, and not have to worry about the partitioning of users, but some hundred thousand mailboxes (Maildir) in the same filesystem has me a bit scared for what would happen in a disaster situation. Full restore from backup would take ages. So we're looking at splitting it up into many smaller filesystems. Still clustered and accessible from all POP/IMAP-servers. We will also start making users more sticky to each server, to get cache effects. First POP/IMAP sessions will be made sticky trough "dovecot director", and later we will probably also make message delivery sticky by telling postfix to deliver via LMTP trough the same director. -jf
