linux-kernel - ext2 + -osync: not as easy as it seems

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Message-ID: <20090113131418.GD30352@atrey.karlin.mff.cuni.cz>
Date:	Tue, 13 Jan 2009 14:14:18 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	kernel list <linux-kernel@...r.kernel.org>, jack@...e.cz,
	tytso@....edu
Subject: ext2 + -osync: not as easy as it seems

Hi!

I tried to use ext2+ -osync, and was surprised that my data do not hit
the (SATA) disk. Fortunately I soon realized that I need hdparm -W0
/dev/sda.

Could the ext2 be teached to use barriers? -W0 hurts performance more
than neccessary...

Plus it has a nasty behaviour where it reverts to -W1 if disk
connection is momentarily lost. (If you unplug/replug SATA disk, linux
will happily rediscover and use it, but -W0 was already forgotten at
that point, right?)
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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