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/0 208.92.169.4.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. Matt
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/0 208.92.169.4.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. >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`
Matt schrieb:> 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/0 208.92.169.4.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. > > Matt > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos >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. cheers, Rainer
Matt wrote:> I have an email server running Exim, Dovecot, Spamassassin, Clam, etc.Firstly, I'd drop dovecot completely, cyrus-imapd has, for me, been a lot faster and better optimised for situations where you have more than a few hand full of users. Secondly, exim configs out of the box on CentOS are *really* not optimized for performance at all. If you handle more than a few thousand emails an hour, I dont be surprised if exim is to blame for jamming your i/o pipe just trying to work out which email to attempt delivery for next. -- Karanbir Singh : http://www.karan.org/ : 2522219 at icq