Not if the disk drive just *ignores* barrier and flush-cache commands
and returns success. Some consumer drives really do exactly that.
That's the issue that people are asking ZFS to work around.
Can someone please name a specific device (vendor + model + firmware
revision) that does this? I see this claim thrown around like fact
repeatedly, and yet I've never personally experienced an actual
"consumer" device that discarded FLUSH CACHE (EXT) before, and nobody
I know can name one that did.
The only exceptions that might "appear" to be ignoring a barrier that
I've witnessed are "high fly" writes in rotating drives, where the
servo system couldn't detect that the head struck a defect and was
deflected too high to write, and devices that don't support the
command at all (and thus abort 51/04 attempts to flush the cache).
BTW, funky/busted bridge hardware in external USB devices don't count.
I'm more interested in major rotating drive vendors... Seagate/Maxtor,
WD, Hitachi/IBM, Fujitsu, Toshiba, etc.