Re: Er.... for Sendmail users......enough

On Tue, 29 Aug 2006, Damien Hull wrote:

> Joshua J. Kugler wrote:
> > On Tuesday 29 August 2006 09:43, Matthew Schumacher wrote:
> >
> >> Leif Sawyer wrote:
> >>
> >>> Oh, man. I <3 iSCSI via NetApp. It's very smooth.
> >>>
> >> I have been wanting to move to an iscsi san for some stuff at AP&T but
> >> haven't ever played with it. What do you think of it? Does it live up
> >> to the hype?
> >>
> >
> > Let me insert a plug for ATA over Ethernet here. Blazing fast, and rock-solid
> > reliable, in all my tests.
> >
> > j
> >
> >
> It's nice to here this technology works. I don't have a use for it yet
> but I'm working on it. Most of the networks I deal with are small.
> However, I have been thinking about large mail systems. One where you
> farm out SMTP and IMAP. The big question is where do you store the
> email? I was thinking it could be done over NFS. According to some on
> the list this is a bad idea.
>
> Maybe ATA over Ethernet is the way to go. There's also iSCSI. I have no
> idea what that is.
>
> I'm also looking into large terminal server deployments. Lets say you
> have three terminal servers and one file server. All data is stored on
> the file server and mounted across the network. Again I was thinking of
> mounting the home directory using NFS. Maybe iSCSI or ATA over Ethernet
> is the way to go.
>
> So much new technology and no time to learn.

NFS storage is nice, because if you are running a NFS safe, multi-access
safe mailstore (true maildir or maildir+) you are free to load share
across many servers.

For example, netapp based NFS store with Courier IMAP running on 4 to 8
servers. Any server can handle any mailbox, no special configs, or
redirect proxies required.

Cyrus is nice, and they are right when they say that mailbox access is
faster/lower overhead. However, the indexing/etc that makes things
faster/lower overhead limits mailstore access to a single server at a
time, and it is not NFS safe.

You can of course have an iSCSI or similar share, but it can only me live
on one system at a time.

For *very large* mail systems you end up with

Pairs of Cyrus servers acting as hot and standby for a shared SCSI or
iSCSI target. Each server pair handles a subset of the users. Proxy
redirectors send the user session to the correct back end server. If a
server fails that subset of users is offline till the standby takes over.

OR

NetApp/other based NFS shares, with a hashed maildir directory tree. The
tree can be on one netapp, or spread across multiple units for performance
reasons (already assuming netapp == netapp cluster with FC-AL takeover).
Since true maildir is lockless and multi-access/NFS safe you can
have 10 - 20 Courier servers, all mounting the tree, and any system is
able to handle any account. No proxy-redirection required. Same applies
on the delivery side, any SMTP host can deliver to any account.

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Received on Wed Aug 30 15:58:52 2006