From: "Roger Heflin" <rheflin@atipa.com>
Subject: RE: NFS tuning - high performance throughput.
Date: Wed, 15 Jun 2005 14:52:10 -0500
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Cc: "'M. Todd Smith'" <todd@sohovfx.com>, <nfs@lists.sourceforge.net>
To: "'Dan Stromberg'" <strombrg@dcs.nac.uci.edu>
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The mount/remount (unless you time how long it takes to unmount),
will potentially still skew the write test, and the writes
will still be happening for quite a while after the dd completes.
 
                        Roger 

> -----Original Message-----
> From: Dan Stromberg [mailto:strombrg@dcs.nac.uci.edu] 
> Sent: Wednesday, June 15, 2005 2:14 PM
> To: Roger Heflin
> Cc: 'M. Todd Smith'; nfs@lists.sourceforge.net; 
> strombrg@dcs.nac.uci.edu
> Subject: RE: [NFS] NFS tuning - high performance throughput.
> 
> 
> A bigger dd test should work - if you use about 3x your 
> physical memory, you'll probably be fine doing it that way.
> 
> Another way that may work better in -some- cases, is to 
> umount the filesystem and re-mount it - except for warm 
> restartable filesystems.
> 
> On Wed, 2005-06-15 at 10:28 -0500, Roger Heflin wrote:
> > Make the dd test bigger, with 2x the memory size, 50% will be from 
> > cache and almost instanteous, with 4x the memory size, 25% will be 
> > from cache, bigger runs will get closer to actual reality, on the 
> > tests I do I run things 8x, but if you run 2x, 4x, 8x memory you 
> > should get a decent graph to give you an idea of what the 
> actual value 
> > is.
> > 
> >                Roger
> > 		   Atipa Technologies. 
> > 
> > > -----Original Message-----
> > > From: nfs-admin@lists.sourceforge.net 
> > > [mailto:nfs-admin@lists.sourceforge.net] On Behalf Of M. 
> Todd Smith
> > > Sent: Wednesday, June 15, 2005 9:47 AM
> > > To: nfs@lists.sourceforge.net
> > > Subject: Re: [NFS] NFS tuning - high performance throughput.
> > > 
> > > Roger Heflin wrote:
> > > 
> > > >Are you using the same dd test on the local machine test?  
> > > If so cache
> > > >will be a major factor.
> > > >
> > > >Also, raid5 stripe size, bigger is almost always better, 
> I would do 
> > > >some testing with different strip sizes and see how it 
> affects the 
> > > >speed, I have never seen less than 32k be faster than 32k.
> > > >
> > > >Are you using md for the raid5 setup or something else 
> that has not 
> > > >been mentioned?
> > > >
> > > >                     Roger
> > > >  
> > > >
> > > Roger,
> > > 
> > > I was told by a consultant we hired to help us with this that 5Gb 
> > > test files should be large enough to blow out the caches.
> > >  Looking back I realize that must have been when we only 
> had 2Gb RAM 
> > > in the machine ..
> > > is there a better test I can use to check local rw 
> performance, as 
> > > well is there a formula or recommended way to calculate how big a 
> > > file you should rw to properly check local rw?
> > > 
> > > I'll have to ask our soft eng who worked with the 
> consultant as to 
> > > why that particular stripe size was used.  I believe we are using 
> > > md, we attempted to use LVM but ran into some problems 
> and had some 
> > > file inconsistencies that were unacceptable so had to back out of 
> > > it.
> > > 
> > > Cheers
> > > Todd
> > > 
> > > --
> > > Systems Administrator
> > > ----------------------------------
> > > Soho VFX - Visual Effects Studio
> > > 99 Atlantic Avenue, Suite 303
> > > Toronto, Ontario, M6K 3J8
> > > (416) 516-7863
> > > http://www.sohovfx.com
> > > ----------------------------------
> > > 
> > > 
> > >  
> > > 
> > > 
> > > 
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