Re: specify agsize?

Dave Chinner
2013-07-15T01:07:34Z

On Sun, Jul 14, 2013 at 02:06:43AM -0500, Stan Hoeppner wrote:
> On 7/13/2013 11:20 PM, aurfalien wrote:
> ...
> >>> mkfs.xfs -f -l size=512m -d su=128k,sw=14 /dev/mapper/vg_doofus_data-lv_data
> ...
> >>> meta-data=/dev/mapper/vg_doofus_data-lv_data isize=256 agcount=32, agsize=209428640 blks
> >>> = sectsz=512 attr=2, projid32bit=0
> >>> data = bsize=4096 blocks=6701716480, imaxpct=5
> >>> = sunit=32 swidth=448 blks
> >>> naming =version 2 bsize=4096 ascii-ci=0
> >>> log =internal log bsize=4096 blocks=131072, version=2
> >>> = sectsz=512 sunit=32 blks, lazy-count=1
> >>> realtime =none extsz=4096 blocks=0, rtextents=0
> ...
> > Autodesk has this software called Flame which requires very very fast local storage using XFS.
>
> If "Flame" does any random writes then you probably shouldn't be using
> RAID6.

Oh, we are talking about flame/smoke/lustre rendering environments
here. Go back 5 years, a renderwall compositing effects via smoke
was one of the nastiest small random write workloads you could
throw at a filesystem. It was often used to benchmark file server
performance for renderwalls and still may be. Think of a workload
that reads lots of shared texture files across thousands of
machines, each crunching a single video frame to add an effect and
all doing small random writes to the video frame as it modifies a
small section of each line of the video frame....

Translation: tuning for AG size is a waste of time.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com