Subject: Re: RAID controller safety
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Kenny Simpson <theonetruekenny@yahoo.com>
Cc: linux kernel <linux-kernel@vger.kernel.org>
In-Reply-To: <20051230161805.64631.qmail@web34110.mail.mud.yahoo.com>
References: <20051230161805.64631.qmail@web34110.mail.mud.yahoo.com>
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Date: Fri, 30 Dec 2005 18:20:30 +0000
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On Gwe, 2005-12-30 at 08:18 -0800, Kenny Simpson wrote:
> That's what I read in the comments too, but looking at the code I only ever see it set to
> write-back.  I verified this with blktool - our controllers have no battery, and blktool showed
> the i2o-wcache state as write-back.

blktool doesn't support i2o control as far as I am aware. The blk level
generic ioctls are just too crude to control it properly.

> However, I was also told that the i2o_block driver lacks barrier support, so even in the
> write-back case, the controller won't be told to flush/sync.

Correct, but it should only ever enable this in the battery backed case.
Otherwise it uses the per command control bits to decide what mode it
wishes to use for each I/O

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