Re: High load average mail server 5.3-RELEASE

From: Mariano Benedettini (marianobe_at_gmx.net)
Date: 09/24/05

  • Next message: martinko: "Re: Finding what's causing I/O" 
    Date: Sat, 24 Sep 2005 15:16:46 -0300
To: Eric Anderson <anderson@centtech.com>

    I've found on discussion lists that some people also tested values near
    80 or 100. I think I have CPU and RAM to start with a value of 50.
    The rsize and wsize values are both 32768.

    Thanks in advance,
    Mariano.

    Eric Anderson wrote:
    > 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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