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Old 03-13-2010, 10:33 AM   #1
WojtekO
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Distribution: CentOS 5
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High Load @ Mail Server


Code:
top - 14:14:52 up 322 days, 20:24,  2 users,  load average: 46.25, 27.48, 13.28
Tasks: 341 total,   1 running, 340 sleeping,   0 stopped,   0 zombie
Cpu(s):  1.7%us,  0.4%sy,  0.0%ni, 49.6%id, 48.3%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   4146852k total,  3987340k used,   159512k free,   103432k buffers
Swap:  2096472k total,    34224k used,  2062248k free,  3147252k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
29654 popuser   20   0  5888 2304  684 S    5  0.1   0:00.14 pop3d
25595 popuser   20   0  9556 3536  924 D    3  0.1   0:20.66 imapd
25562 popuser   20   0  9556 3532  928 D    2  0.1   0:19.05 imapd
24225 popuser   20   0 11424 5480  928 D    1  0.1   0:24.71 imapd
 8956 root      20   0  2404 1188  796 R    0  0.0   0:06.32 top
    1 root      20   0  2112  632  544 S    0  0.0   1:45.37 init
    2 root      15  -5     0    0    0 S    0  0.0   0:00.07 kthreadd
    3 root      RT  -5     0    0    0 S    0  0.0   0:09.84 migration/0
    4 root      15  -5     0    0    0 S    0  0.0  14:34.70 ksoftirqd/0
    5 root      RT  -5     0    0    0 S    0  0.0   0:03.75 watchdog/0
    6 root      RT  -5     0    0    0 S    0  0.0   0:47.06 migration/1
    7 root      15  -5     0    0    0 S    0  0.0  14:10.59 ksoftirqd/1
At the time of the above top, netstat reported:
16 Established :25 connections
16 Established :993 connections
5 Established :110 connections

The server is a dual xeon 8-core with 4gb of ram.


We've got a new problem with our mail server where we have load spikes that reach 50-70 (usual load is 2-3)

During those load spikes the server becomes unresponsive to SNMP requests and times out for any new mail connections and our users have been complaining about that.

How would you verify what is causing this high load? What should I start with?
 
Old 03-13-2010, 10:41 AM   #2
AlucardZero
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48.3%wa -> half of your processing time is spent waiting for I/O.
three imapd in state 'D' -> your IMAP daemons are in uninterruptible sleep waiting for I/O.

I'd check what imapd is opening, your storage devices and mount points. Maybe a hard drive is going or you store mail on an NFS share and it's being slow.
 
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Old 03-13-2010, 11:21 AM   #3
WojtekO
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Thank you for your analysis.
There are no NFS shares on this server. All mail resides on the local hard disk.

I'll try running iostat during the next high load occurrence to see if it can give any pertinent information.
 
Old 02-02-2011, 12:19 PM   #4
copperkin
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Unhappy Were you able to fix it?

Were you able to fix this problem? I am facing the same exact situation
 
  


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