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.
