[wplug] Hardware RAID tuning

[Martin James Gehrke]

from: http://www.directron.com/expressguide.html

way more than you are using.

in a single direction PCI-E 4x has 2000MB/s




On Thu, Jun 16, 2011 at 11:02 AM, Matthew Zwier <mczwier at gmail.com> wrote:

> And by PCI I mean PCI Express.
>
> On Thu, Jun 16, 2011 at 11:00 AM, Matthew Zwier <mczwier at gmail.com> wrote:
> > On Wed, Jun 15, 2011 at 10:17 PM, Drew from Zhrodague
> > <drewzhrodague at zhrodague.net> wrote:
> >>        Shouldn't you not share controllers with other arrays, and
> actually use
> >> multiple controllers per array? This is how we did things back in the
> >> day with old JBOD Suns -- stripe across disks and stripe across
> >> controllers. Modern architectures turn everything on their ears, so I
> >> could be missing something.
> >
> > I doubt you're missing something, but we're out of slots in the
> > server, and out of space in the rack for a new one :)  Did I mention
> > this is a scientific computing cluster for a small research group?
> > Funds and space are limited.  Also, I can't correlate the performance
> > drop to a specific load on the other array.
> >
> >>        If it helps, I've found that a straight scp in Amazon's cloud is
> faster
> >> than an scp -C or compressed rsync. The results may be different with a
> >> hardware environment, but testing is the only way to be sure.
> >
> > Yeah, tested this yesterday.  Compression slows things down
> > considerably, Enumerating files (rsync) slows things down to kilobytes
> > per second.  A typical user has a million or so tiny files and a few
> > hundred (10 GB - 200 GB) very large files.  xfsdump over an
> > uncompressed ssh connection appears the way to go.
> >
> > Interestingly, piping things through bar to measure throughput seems
> > to slow things down a *lot*, and in fact may be the greater reason for
> > the intermittent throughput -- I'm sustaining 4 MB/s - 50 MB/s,
> > seemingly correlated to what set of files xfsdump is working on, now
> > that I don't have bar in the pipe.  I'm wondering if I need to do
> > something *really* dumb, like xfsdump -J - | xfsrestore -J -
> > /some/nfs/mount.  That would seem to be going through one fewer
> > userland buffers.
> >
> > Hmm...what's the bandwidth of a PCI bus?
> >
> > MZ
> >
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