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From: <Ivan.Novick@emc.com>
Date: Tue, 16 Nov 2010 16:56:00 -0500
Subject: allocsize mount option behavior
Message-ID: <C9083DF0.FCE%ivan.novick@emc.com>
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Cc: Timothy.Heath@emc.com

Hello,

I am using the allocsize mount option to reduce fragmentation, by ensuring =
extents are of a minimum size.

Under a workload with heavy concurrency we noticed that disk space usage we=
nt up noticeably.

Can someone clarify the expected behavior of allocsize.  Does it force file=
s to be at least the allocsize size on disk, or is the allocsize size reser=
ved for each open file and then freed up if it is not used and the file is =
closed, or does it work some other way.

For example if allocsize=3D1g and I open 1000 files and start writing a sma=
ll amount of data to each file =85. Would the device show as using 1000* 1g=
 of disk space while the files are opened and after they are closed then on=
ly the amount of space actually written by the user would be shown as used =
on disk?

Cheers,
Ivan Novick

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