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Re: specify agsize?

To: Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
Subject: Re: specify agsize?
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Mon, 15 Jul 2013 11:07:22 +1000
Cc: aurfalien <aurfalien@xxxxxxxxx>, Eric Sandeen <sandeen@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <51E24E03.8010609@xxxxxxxxxxxxxxxxx>
References: <6A14EB72-A699-47AF-937D-D6DA1CF12ACB@xxxxxxxxx> <51E2092D.7090409@xxxxxxxxxxx> <9AB8D1D3-29D7-4C43-A624-37024CA4EFD9@xxxxxxxxx> <51E24E03.8010609@xxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
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.


Dave Chinner

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