XFS: performance

[Dave Chinner]

On Mon, Nov 29, 2010 at 10:50:33PM -0600, Stan Hoeppner wrote:
> Dave Chinner put forth on 11/29/2010 10:29 PM:
> > On Sun, Nov 28, 2010 at 11:41:35PM -0600, Stan Hoeppner wrote:
> >> Yclept Nemo put forth on 11/28/2010 9:57 PM:
> >>> You mention an eight-core machine (8c?). Since I operate a dual-core
> >>> system, would it make sense to increase my AG count slightly, to five
> >>> or six?
> >>
> >> Dave didn't mention the disk configuration of his "workstation".  I'm
> >> guessing he's got a local RAID setup with 8-16 drives.
> > 
> > 2 SSDs in RAID0.
> 
> From an IOPs and throughput perspective, very similar to my guess.
> Curious, are those Intel, OCZ, or other SSDs?  Which model,
> specifically?  Benchmark data?  I ask as all the results I find on the
> web for SSDs are from Windows 7 machines. :(  I like to see some Linux
> results.

Cheap as it gets 120GB Sandforce 1200 drives. In RAID0, I'm getting about
450MB/s sequential write, a little more for read. I'm seeing up to
12-14k random 4k writes per drive through XFS. Other than that I
didn't bother with any more benchmarks because it was clearly Fast
Enough.

> > And to point out the not-so-obvious, this is the _default layout_
> > that mkfs.xfs in the debian squeeze installer came up with. IOWs,
> > mkfs.xfs did exactly what I wanted without me having to tweak
> > _anything_.
> 
> Forgive me for I've not looked at the code.  How exactly does mkfs.xfs
> determine the AG count?  If you'd had a single 7.2k SATA drive instead
> of 2 RAID0 SSDs, would it have still given you 16 AGs?  If so, I'd say
> that's a bug.

No, it detected the RAID configuration. 16 AGs is the default for a
RAID device, 4 AGs is used if RAID is not detected.

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com