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Date: Fri, 22 Apr 2011 06:25:26 +1000
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From: ronnie sahlberg <ronniesahlberg@gmail.com>
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Subject: Re: [Qemu-devel] iSCSI support for QEMU
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To: Christoph Hellwig <hch@lst.de>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, stefanha@linux.vnet.ibm.com

On Thu, Apr 21, 2011 at 10:49 PM, Christoph Hellwig <hch@lst.de> wrote:
> On Thu, Apr 21, 2011 at 09:36:12PM +1000, ronnie sahlberg wrote:
>> There are some high-volume arrays that advertise support but fail any
>> cdb with FUA, FUA_NV bits set with sense, so it needs to be made optiona=
l.
>
> Which on would that be? =A0Linux uses the FUA bit if the device advertise=
s support
> via the DPOFUA bit since 2005, and prints a warning if a FUA write fails,
> and since last year even fails the request hard. =A0I'd be really surpris=
ed
> if a common device fails FUA writes and we didn't know about it by now.
>
> Either way you'll have to still guarantee data made it to non-volatile
> storage for cache=3Dwritethrough mode, either by disabling the WCE bit
> using MODE SELECT, or by flushing the cache after every write.
>

Thankyou for your patience.
I understand and I have updated the patch to set FUA when the _WB flag
is not set.

regards
ronnie sahlberg