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Re: Mail server

On Mon, 24 Feb 2003 20:59, Rich Puhek wrote:
> Russell Coker wrote:
> > I have been considering modifying the Qmail and maildrop code to not use
> > fsync() etc to allow more users per server (yes I know about the
> > reliability issues, but there are lots of more important things to worry
> > about).
> Are you using mboxes under /var/spool/mail, or are you using Maildirs
> under /home?

Maildir's in home directories on a file system dedicated for the task.

> If you're using the latter, wouldn't it be easier (and safer) to spread
> your home dirs across multiple hard drives (or, more appropriately,
> multiple RAID partitions on different disks?) Of course, IIRC, the 2650
> is a 2U server, so you're limited to what you can cram into the box.

The 2650 contains 5 hard drives, that's a RAID-5 of 4 disks plus one hot-spare 
disk.  Therefore only one partition for all the storage.

> In your particular configuration, have you looked at the
> advantages/disadvantages of having something like two disks in RAID 1
> and another 2 or more disks in another RAID set (1 or 5, depending on #
> of drives) with the mail spool on one RAID set and the rest of the
> filesystems (including /var) on the other?

For only 4 active disks I don't expect any great performance benefit from 
that, and probably a performance loss at times when one array is busy and the 
other is idle.

For 10+ disks I would probably look at a RAID-1 for the spool with the journal 
on a nvram device and the rest of the disks in a RAID-5 for storage.

> Just asking because I have a similar setup to yours (one big HW RAID-5)
> and have been wondering if that's the best way to go.

If you have an excessive number of disks in the RAID-5 then the OS may not be 
able to send enough IO requests to it.  I don't think that file systems in 
Linux (with the possible exception of XFS) could deliver good performance on 
a RAID array of 100 disks.  Delivering good performance on 10 file systems 
that each have 10 disks is much easier to achieve if your data store can 
easily be striped over 10 file systems (as it can be for mail).

A previous mail server I worked on had 192 disks divided into 10 RAID sets for 
mail storage for this reason.  I am not sure how many of the 192 disks were 
used and how many were spare.  I suspect that it was 180 disks in use and 12 

http://www.coker.com.au/selinux/   My NSA Security Enhanced Linux packages
http://www.coker.com.au/bonnie++/  Bonnie++ hard drive benchmark
http://www.coker.com.au/postal/    Postal SMTP/POP benchmark
http://www.coker.com.au/~russell/  My home page

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