On Thu, Apr 21, 2011 at 10:49 PM, Christoph Hellwig <h...@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
