On Sat, Dec 15, 2007 at 10:35:20PM -0600, Eric Sandeen wrote:
> Alex Madarasz wrote:
> > We're building a new Fedora 8.0.1 Linux system to stream data from a
> > 250Msps ADC to disk, and want to start tuning the system configuration
> > for maximum XFS write performance. To date, without any significant
> > effort at tuning our Fedora 7 dev system, we're seeing 250MBps write
> > with 8-bit samples and ~ 300MBps write with 16-bit samples. We want to
> > push the tuning as far as we can go with this architecture before we
> > start looking at other hardware options. Looking at various other
> > tuning pages on the Web finds few that are interested in maxing out
> > sequential writes to very large arrays while using SAS HW RAID with big
> > fast SAS drives too.
>
> ...
>
> > XFS Tuning Options?
> >
> > - HW RAID0:
> > - Array/logical disk HW RAID stripe size?
>
> At any rate you'll want to match xfs's geometry with the raid geometry.
>
> > - Cache enabled (some reports that cache s/b turned off?)?
>
> If it's battery-backed cache, leave it on, and disable barriers in xfs
> (it's a mount option)
>
> > - xfs mkfs / mount options?
>
> David mentioned these before as a generic place to start:
>
> # mkfs.xfs -f -l lazy-count=1,version=2,size=128m -i attr=2 -d agcount=4
> <dev>
> # mount -o logbsize=256k <dev> <mtpt>
>
> and that those would be upcoming new defaults for mkfs.
>
> 4 ags may not be what you want for a ~2T filesystem.
Right - the 4 AG tuning is effectively for single disk configurations to
limit parallelism and therefore keep seeks between AGs down. When you
have multiple disks, the [new] mkfs defaults should be just fine (i.e.
just drop the agcount suggestion).
Cheers,
Dave.
--
Dave Chinner
Principal Engineer
SGI Australian Software Group
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