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Re: allocsize mount option, was: [PATCH 1/2] xfs: dynamic speculative EO

To: xfs@xxxxxxxxxxx
Subject: Re: allocsize mount option, was: [PATCH 1/2] xfs: dynamic speculative EOF preallocation
From: Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxxxxx>
Date: Fri, 15 Oct 2010 08:51:24 +0200
In-reply-to: <20101014213325.GF4681@dastard>
Organization: it-management http://it-management.at
References: <1286187236-16682-1-git-send-email-david@xxxxxxxxxxxxx> <1287076965.2362.520.camel@doink> <20101014213325.GF4681@dastard>
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On Donnerstag, 14. Oktober 2010 Dave Chinner wrote:
> > I guess the reason one might want the "allocsize" mount
> > option now becomes the opposite of why one might have
> > wanted it before.  I.e., it would be used to reduce
> > the size of the preallocated range beyond EOF, which I
> > could envision might be reasonable in some circumstances.
> 
> It now becomes the minimum preallocation size, rather than both the
> minimum and the maximum....

Until now, I often set allocsize to be <nr of data disks>*<stripe size>, 
i.e. in a 8 disk RAID-6 with 64KB stripe size = 6*64 = 384KB
I guess this should provide the best performance.

Is my assumption true?
Will it change with the new code?
Does XFS automatically use allocsize=<1 full stripe> so I can skip my 
manual allocsize options?

-- 
mit freundlichen Grüssen,
Michael Monnerie, Ing. BSc

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