Extreme performance falling on ZFS by durable operation of a server

[K. Macy]

Hi Alexandr,

- How much memory do you have?

- What are your ARC settings?

Thanks,
Kip

On Thu, Apr 8, 2010 at 8:32 AM, Alexandr D. Sergeev <ales at ripn.net> wrote:
> Hi, all!
>
> There are problems with a server on FreeBSD 7.2 CURRENT (6 Jul 2009), carrying out the task of mail server SMTP, IMAP.
>
> Messages are stored in maildirs on file system ZFS (mirror of 2 SAS 3k drives).
> Dovecot is used as IMAP server.
>
> After reboot the system works perfectly, however, somewhere in a month, at the same load, arise periodic long delays at opening of new letters.
>
> Judging by output iostat -x -w 1, during these moments the disk subsystem is strongly loaded.
> %busy disks comes nearer to 100 %. Readings nearby 300 per sec prevail. and approx. 10MBytes per sec.
>
> Somebody can advise, what diagnostics needed, for understanding of the reason of problems?
>
> There is an opinion that a problem with ZFS.
>
> Probably, it does not have enough memory. Because during the periods of occurrence of a problem,  ARC is have less 300MB:
>
> vmstat -m
> ...
>      solaris 1245732 274745K       - 25872717949  16,32,64,128,256,512,1024,2048,4096
> ...
>
> Or it is bug of ZFS implementation.
>
> --
> Best regards,
> Alexandr D.Sergeev
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