High load average mail server 5.3-RELEASE

[Eric Anderson]

Mariano Benedettini wrote:
> Thanks for all the replies. It's not a HD problem.
> On monday I'll increase the number of nfsd processes and the number of 
> nfsiod on the client, setting both to 50,
> I think that the nfs performance will be much better :-)

50 nfsiod's may be a bit overkill, but you should experiment to find out.

You should also increase the rsize and wsize parameters on the mount 
options for better efficiency.

Eric



> Eric Anderson wrote:
> 
>> Francisco Reyes wrote:
>>
>>> On Tue, 13 Sep 2005, mariano benedettini wrote:
>>>
>>>> 91.3% idle
>>>
>>>
>>>
>>>
>>> CPU is not the problem. :-)
>>>
>>>
>>>> Mem: 1599M Active, 1704M Inact, 311M Wired, 189M Cache, 112M Buf, 
>>>> 14M Free
>>>> Swap: 2023M Total, 184K Used, 2023M Free
>>>
>>>
>>>
>>>
>>> Swap is not the problem.
>>>
>>>
>>> Do
>>> vmstat 10
>>>
>>> Watch the output.
>>> In particular look at the first 3 columns.
>>>  procs
>>>  r b w
>>>  1 1 0
>>>  0 1 0
>>>  1 1 0
>>>
>>> The left most column is CPU, the second column is disk IO.
>>>
>>> If you have a number in the "b" column and it never hits 0 you have 
>>> an I/O problem. You HDs are not catching up.
>>>
>>> If you are using NFS and the "b" colun is not high and hits 0 
>>> some/all the time then the bottleneck is either the nfs connection or 
>>> the nfs server.
>>>
>>> For example I have some servers that the "b" column would be between 
>>> 20 and 60 for a while. I am currently working on removing some of the 
>>> load of the machine. In my case more memory would help, but the 
>>> computer vendor we bought the machine from has sent us the wrong 
>>> memory 3 TIMES!!
>>
>>
>>
>> Also, if it is an NFS server, one should check the cpu times on the 
>> nfsd processes.  I've found that many times there aren't enough nfsd 
>> processes to take the load from many clients.  Increasing the number 
>> (double it) often helps this.  The max in 5.3 is 20, but you can 
>> easily change it and get around it.
>>
>> Eric
>>
>>
>>
>>


-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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