Cyrus IMAP on NFS

[Paolo Cravero]

Hello.

>  I know this is a very tipical question but... nowadays... how does Cyrus
> IMAP work with NFS 4?. It supports file locking and I would only mount
> each mail spool in an own unique server... so
> 
>  I think it should be very similar to using a local filesystem... Does
> anyone can tell some experience in this config?..

It works, but you must know what you're doing. First of all: keep metadata
on a local filesystem because that's where most of the action happens.
Messages can then reside on NFS, and all documented considerations still
hold true: risk of loosing connection, network bottleneck, FS going
read-only. There may be more, but in today's world of virtual servers it is
hard to think of local storage as "physically attached set of disks" and
something can go wrong in many hidden places anyway.

If the partition is tied to just one server most probably you will not have
contention problems. Troubles occur if the NFS goes away (ie not remounted
after reboot) and Cyrus rebuilds the tree under local disks, so you must be
quick to intercept that condition.

NFS can be an option to keep online old messages, especially if it costs
much less than your other storage. Since those messages are usually accessed
very rarely, network is not a real bottleneck and you are left with TCP/IP
issues. But do keep metadata (and indexes) on local disks.

>From our storage admins: "One advantage of having most of the
obsolete-but-keep-it-i-might-need-it-one-day data not on a local filesystem
is that in the rare event of system crash you will not have to wait for fsck
to complete, as it must be done for local disks. If you have TB's it makes
quite a difference."


Paolo
(sitting on few NFS spools)