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Re: howto preallocate to minimize fragmentation

To: Eric Sandeen <sandeen@xxxxxxx>
Subject: Re: howto preallocate to minimize fragmentation
From: Ying-Hung Chen <ying@xxxxxxxxxxxxxx>
Date: Thu, 22 Sep 2005 22:56:54 +0800
Cc: linux-xfs@xxxxxxxxxxx
In-reply-to: <4332C248.70503@xxxxxxx>
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> pre-allocation before writing would still be your best bet.  If you
> pre-allocate on a fresh fs before writing, you should get very large
> extents.

does this mean, if I create a 2GB file via dd (not sparse file), when i
'overwrite' to the same file, it will stay there? (same physical place)
> 
> Other things you could try; if you put each file in its own dir, it will
> tend to go into its own allocation group.
> 
> You could make the filesystem with allocation groups sized at 2GB
> 

I just thought of wild idea... since i am creating 90 files, what if i
just create 90 allocation group via -d agcount=90, does this make sense
or it won't work at all?

Thanks,

-Ying


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