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Re: LWN.net article: creating 1 billion files -> XFS looses

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Subject: Re: LWN.net article: creating 1 billion files -> XFS looses
From: Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxxxxx>
Date: Tue, 7 Sep 2010 08:20:07 +0200
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
In-reply-to: <20100907033134.GF7362@dastard>
Organization: it-management http://it-management.at
References: <201008191312.49346@xxxxxx> <201009070058.40849@xxxxxx> <20100907033134.GF7362@dastard>
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On Dienstag, 7. September 2010 Dave Chinner wrote:
> # mkfs.xfs -n size=64k
> (-n = naming = directories. -d = data != directories)

Thank you, Dave. Do I interpret that parameter right:

When a new directory is created, per default it would occupy only 4KB, 
with -n size=64k would be reserved. As the directory fills, space within 
that block will be used, so in the default case after 4KB (how many 
inodes would that be roughly? 256 Bytes/Inode, so 16 entries?) XFS would 
reserve the next block, but in your case 256 entries would fit.

That would keep dir fragmentation lower, and with todays disks, take a 
minimal more space, so it sounds very good to use that option. 
Especially with RAIDs, where stripes usually are 64KB or bigger. Or 
would the waste of space be so big that it could hurt?

Last question: Is there a way to set that option on a given XFS?

-- 
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Michael Monnerie, Ing. BSc

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