>> 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@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@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`
Right now its running pretty good but here it is.
[root@server ~]# w
13:11:02 up 3:08, 2 users, load average: 4.03, 5.71, 5.51
avg-cpu: %user %nice %sys %iowait %idle
2.80 0.00 1.60 58.10 37.50
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s
avgrq-sz avgqu-sz await svctm %util
sda 0.60 142.80 67.20 170.20 678.40 2292.80 339.20
1146.40 12.52 118.53 615.66 4.21 99.92
sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
sda2 0.60 142.80 67.20 170.20 678.40 2292.80 339.20
1146.40 12.52 118.53 615.66 4.21 99.92
sdb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
sdb1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
dm-0 0.00 0.00 67.40 286.20 678.40 2289.60 339.20
1144.80 8.39 163.02 582.40 2.83 99.94
dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00
sar also.
10:02:56 AM LINUX RESTART
10:10:04 AM CPU %user %nice %system %iowait %idle
10:20:01 AM all 13.87 0.00 2.45 59.20 24.49
10:30:03 AM all 22.26 0.00 3.68 53.51 20.54
10:40:01 AM all 20.58 0.00 3.78 55.40 20.24
10:50:04 AM all 22.20 0.00 5.23 52.67 19.91
11:00:05 AM all 21.58 0.00 4.72 51.81 21.89
11:10:01 AM all 18.14 0.00 4.52 56.91 20.43
11:20:03 AM all 21.42 0.00 4.59 47.20 26.79
11:30:02 AM all 19.22 0.00 4.48 53.86 22.44
11:40:04 AM all 17.59 0.00 4.82 51.61 25.98
11:50:02 AM all 15.88 0.00 4.67 45.74 33.71
12:00:01 PM all 13.32 0.00 2.73 25.72 58.23
12:10:02 PM all 16.98 0.00 4.54 53.14 25.35
12:20:01 PM all 17.31 0.00 3.45 47.80 31.44
12:30:01 PM all 19.45 0.00 4.08 36.47 40.00
12:40:01 PM all 13.79 0.00 4.39 44.83 36.99
12:50:01 PM all 12.18 0.00 3.93 30.16 53.73
01:00:01 PM all 11.53 0.00 2.38 20.96 65.12
Average: all 17.49 0.00 4.03 46.29 32.19
A while after the reboot it straightened its self out. Yesterday "w"
was indicatining load average of like 120 or more at times. Today
after reboot all is good.
Matt
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