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Re: Small files perform much faster on newly formatted fs?

To: xfs@xxxxxxxxxxx
Subject: Re: Small files perform much faster on newly formatted fs?
From: Michael Monnerie <michael.monnerie@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 9 Jun 2011 07:44:12 +0200
Cc: Norbert Veber <nveber@xxxxxxxxxxxxxx>
In-reply-to: <20110608185844.GB28625@xxxxxxxxxxxxxx>
Organization: it-management http://it-management.at
References: <20110607163742.GH28625@xxxxxxxxxxxxxx> <201106081547.38266@xxxxxx> <20110608185844.GB28625@xxxxxxxxxxxxxx>
User-agent: KMail/1.13.6 (Linux/2.6.38.6-zmi; KDE/4.6.0; x86_64; ; )
On Mittwoch, 8. Juni 2011 Norbert Veber wrote:
> I re-created the test filesystem to be the same size (20gb) as the
> original, and copied all the same files to it, so both are now 80%
> full.

But copying data at once leads to "perfectly" aligned data, and cannot 
be compared to a filesystem that has aged over the years. Maybe you can 
compare it like this:
1) remount the old partition with "noikeep"
2) mv /old/* /new
3) cp /new/* /old/

Maybe that would help? I'm interested to find the difference.

Also, as Eric said, both partitions are on different locations on the 
disks, but I guess your old partition is more outside, thus in the 
quicker region, than the new partition. Is that true?

Could it be that the old filesystem gets mounted with different 
logbufs/logbsize values? Would the mount options 
"logbufs=8,logbsize=256k" maybe make a difference?
Is the position of the log area fixed on disk? Maybe that is not stripe 
aligned. Could you check with a newer kernel using "delaylog"?

[Dave wrote]
> Those mount options are ignored if the filesystem doesn't have the
> superblock feature bit set for aligned allocations. A filesystem
> with 0/0 for sunit/swidth does not have the superblock bit set....

And I guess it's not possible to set that bit now?

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

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