[CentOS] RAID on Email Server

John R Pierce pierce at hogranch.com
Fri Oct 10 17:52:08 UTC 2008

Matt wrote:
> 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 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.

can you paste the output of `iostat -x 5 5` while its busy ?   this will 
show definateively how busy your disks are... 

the first sample from vmstat, iostat, etc only shows the AVERAGE since 
the system booted.   the 2nd and beyond samples are the average over the 
time intervals specified (5 5 means 5 seconds, 5 samples)

oh, if you don't have iostat, its part of package sysstat, so `yum 
install sysstat`

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