linux-kernel - Re: Linux 2.6.29

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Message-ID: <49D5347A.8030403@garzik.org>
Date:	Thu, 02 Apr 2009 17:56:10 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	David Rees <drees76@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Janne Grunau <j@...nau.net>,
	Lennart Sorensen <lsorense@...lub.uwaterloo.ca>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Theodore Tso <tytso@....edu>, Jesper Krogh <jesper@...gh.cc>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 2.6.29

David Rees wrote:
> Either way - forcing the data to be synced to disk a couple times
> every second is a hack and causes fragmentation in filesystems without
> delayed allocation.  Fragmentation really goes up if you are recording
> multiple shows at once.

Check out posix_fallocate(3).  Not appropriate for every situation, 
might eat additional disk bandwidth...

But if you are looking to combat fragmentation, pre-allocation (manual 
or kernel-assisted) is a relevant technique.  Plus, overwriting existing 
data blocks is a LOT cheaper than appending to a file.  fsync's more 
quickly to disk, too.

	Jeff


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