Re: [Qemu-devel] iSCSI support for QEMU

[ronnie sahlberg <ronniesahlberg@gmail.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 optional.
>
> Which on would that be?  Linux uses the FUA bit if the device advertises 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.  I'd be really surprised
> 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=writethrough 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