SAN based storage

[Michael Loftis]

--On April 19, 2006 6:40:27 PM +0200 Andrzej Kwiatkowski 
<andrzej.kwiatkowski at gmail.com> wrote:

> Hi
>
> I'm going to build email-system based on cyrus with SAN storage.
> As an array i will use CX700.
>
> For every instance i'g going to build raid group from 9 146GB disks.
>
> I've noticed that in last version of imapd is possibility to separate
> mail files and meta files.
>
> Does it make sense to seperate mailboxes and metafiles, and/or sieve
> files, mboxlist partiotion
> when using SAN storage with big performance ?
>
> I know that with normal disk this is very important,
> bot it this situation i this this make no sense.

If you mean separate filesystems, I'd tend to say yes still, depending on 
your base OS.  Linux for example keeps queues and caches in different ways 
than Solaris.  Irregardless of what OS you use you'll want some volume 
management, and a filesystem that can atleast grow online such as ReiserFS. 
I've heard that ext3 can be resized online, but I've never seen it myself 
so can't say one way or the other there.

I've got one installation backed by a CX200 and the only issue we run into 
is I/O loading when we had the mail queues and the backend storage all on 
the same spindles.  Once I seperated those out things got a lot better. 
We're talking quite a bit of I/O though, and the main mail store spindles 
also back part of the NFS server cluster as well.

We use a Linux 2.4 kernel, ReiserFS, on top of LVM, on top of MD in 
multipath mode -- the reason for the MD multipath is at the time there 
wasn't a working qlogic driver with builtin failover support.