[CentOS] RAID on Email Server
rainer at ultra-secure.de
Fri Oct 10 21:42:15 UTC 2008
> I have an email server running Exim, Dovecot, Spamassassin, Clam, etc.
> on Centos 4.x 32bit. On occasion I have disk I/O problems. Its
> handling several domains and alot of email. Its currently on a single
> SATA drive. I am thinking of moving too 3 drives with RAID 1 for
> redundancy. RAID 1 will help me on reads but do nothing on writes as
> I understand. I am thinking the majority of my I/O is read though
> not? I imagine quotta checks and all that being done and everytime a
> user checks there email every message in the inbox must be read.
> I guess I am asking if RAID 1 will help my I/O problem much?
> [root at server ~]# w
> 12:04:02 up 2:01, 1 user, load average: 7.02, 7.47, 11.84
> USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
> root pts/0 18.104.22.168.ppp 11:25 0.00s 0.02s 0.00s w
> [root at server ~]# vmstat
> procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
> r b swpd free buff cache si so bi bo in cs us sy id wa
> 0 2 0 1558496 456916 1087224 0 0 198 749 795 537 18 4 27 50
> The above is when its running pretty good.
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How many concurrent users?
If you stay with SATA, you will probably have to increase the amount of
disks in you storage-array (depending on the number of users).
A SATA disk does only 80 I/Os per second or so - and clamav+spamassassin
alone will consume a lot of these.
Try to put their working-directories on a swap-backed tmpfs.
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