[Top] [All Lists]

allocsize mount option

To: xfs@xxxxxxxxxxx
Subject: allocsize mount option
From: Gim Leong Chin <chingimleong@xxxxxxxxxxxx>
Date: Tue, 12 Jan 2010 01:25:14 +0800 (SGT)
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com.sg; s=s1024; t=1263230714; bh=Ghr9nAEswDO6TvYvmUaK6gTVlC6cbZ//e+fH4qxFx6A=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=3dJLn3jvSsQLufyM3L/8plxcsYwreWRgQ7OWxP1bfra00BqXpkvvNOJiKGo8cMl3mM3rEHyH8diFoWT9o8wTOcPRfFzAUKSDJO0xMgVLpwCDsFJUrIV78PSD7xdJod4QZ1pkVv8aEuXnW+yBhMX7s5Zb4ZjKyOCze0NBqzIn2m8=
Domainkey-signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.sg; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=0ueFE0aQN5XOehwhMMb6xoRbDYvotnXsnguyEU/US8q5dJaIc9RCf9nsxrKuZeFDd6Utszo/Zu7aZMZxdpB0LOqYZvrfYmfXADXiHTN3pFBc/mTSrUJ1piEHIQHswwB9qybeKPlA7ycChqu+ZRt6oBIDtZ5Pt2tvJbw7r0Yp5k4=;

Mount options for xfs
       Sets  the buffered I/O end-of-file preallocation size when doing delayed 
allocation writeout (default size is 64KiB). 

I read that setting allocsize to a big value can be used to combat filesystem 
fragmentation when writing big files.

I do not understand how allocsize works.  Say I set allocsize=1g, but my file 
size is only 1 MB or even smaller.  Will the rest of the 1 GB file extent be 
allocated, resulting in wasted space and even file fragmentation problem?

Does setting allocsize to a big value result in performance gain when writing 
big files?  Is performance hurt by a big value setting when writing files 
smaller than the allocsize value?

I am setting up a system for HPC, where two different applications have 
different file size characteristics, one writes files of GBs and even 128 GB, 
the other is in MBs to tens of MBs.

I am not able to find documentation on the behaviour of allocsize mount option.

Thank you.

Chin Gim Leong

      New Email names for you! 
Get the Email name you&#39;ve always wanted on the new @ymail and @rocketmail. 
Hurry before someone else does!

<Prev in Thread] Current Thread [Next in Thread>