linux-ext4 - Re: Does ext4 send FUA to flush disk cache

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Message-Id: <DE099CBA-6478-4651-B3E5-F406D0C11C3D@mit.edu>
Date:	Sun, 10 Apr 2011 08:17:58 -0400
From:	Theodore Tso <tytso@....EDU>
To:	Mark Busheman <markbusheman@...il.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: Does ext4 send FUA to flush disk cache


On Apr 8, 2011, at 6:02 PM, Mark Busheman wrote:

> I plan to use data=journal option with ext4. Would like to know if
> ext4 send FUA (Forced Unit Access)
> to flush the disk cache?

FUA doesn't cause a cache flush.   Ext4 does send cache flush commands, or barriers, to make sure the data written to disk is flushed all the way down to the disk platters on transaction commits.

-- Ted

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