Extreme performance falling on ZFS by durable operation of a server

[Alexandr D. Sergeev]

Whether there are any ideas about the reasons of such problems?

Whether transition to FreeBSD 8.0 RELEASE / STABLE can help?
ZFS in it is declared as "bug free"

On Fri, Apr 09, 2010 at 06:44:09AM +0400, Alexandr D. Sergeev wrote:
> On Thu, Apr 08, 2010 at 01:14:42PM -0700, K. Macy wrote:
> > Hi Alexandr,
> 
> Hi Kip,
> 
> > 
> > - How much memory do you have?
> 
> 4Gb.
> Applications consume a lot of memory, is partially used swap (~1Gb, but without active i/o).
> 
> We have planned increase in memory to 16G
> 
> > 
> > - What are your ARC settings?
> 
> Settings is default, that recommended for amd64 kernel.
> But I am not assured that it is optimal.
> Thus sysctl variables are automatically sets to:
> vfs.zfs.arc_max ~800Mb
> vfs.zfs.arc_mim ~128Mb
> 
> Now the next reboot was required.
> Together with which following settings have been made:
> 
> vm.kmem_size=2048M
> vfs.zfs.arc_max=1536M
> vfs.zfs.arc_min=1024M
> vfs.zfs.vdev.cache.size=64M
> 
> Let's look, as it will affect.
> 
> However there is confidence that no problem at a size of ARC.
> Even at 200Mb ARC, productivity should not fall so strongly.
> 
> > 
> > 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
> > > _______________________________________________
> > > freebsd-performance at freebsd.org mailing list
> > > http://lists.freebsd.org/mailman/listinfo/freebsd-performance
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> > >
> 

--
Best regards,
Alexandr D.Sergeev