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Re: allocsize mount option

To: Gim Leong Chin <chingimleong@xxxxxxxxxxxx>
Subject: Re: allocsize mount option
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Thu, 14 Jan 2010 11:42:11 -0600
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <264613.60659.qm@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
References: <264613.60659.qm@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
User-agent: Thunderbird 2.0.0.21 (X11/20090320)
Gim Leong Chin wrote:
> Hi Dave,
> 
> 
>> fragmented, it just means that that there are 19% more fragments 
>> than the ideal. In 4TB of data with 1GB sized files, that would
>> mean there are 4800 extents (average length ~800MB, which is 
>> excellent) instead of the perfect 4000 extents (@1GB each). Hence
>> you can see how misleading this "19% fragmentation" number can be
>> on an extent based filesystem...
> 
> There are many files that are 128 GB.
> 
> When I did the tests with dd on this computer, the 20 GB files had up
> to > 50 extents.

which is at least 400mb per extent, which is really not so bad.

-Eric

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