On Oct 29, 2008, at 2:51 PM, Thor Lancelot Simon wrote:
In practice, this would mean using an ordered tag with SCSI disks (because ordered tags do not complete until all prior simple-tagged commands complete)
Just because a *command* (not a *write*, necessarily) has completed doesn't mean it's on oxide. If you really want to force the simple- tagged writes before the ordered-tag write to be on oxide, your ordered-tag command should be a SYNCHRONIZE CACHE, period (and then you need to hope that your RAID vendor actually supports the command, *sigh*).
and causing a cache flush for IDE disks (at least until we get tagged queueing support for them). I don't know how FUA works for IDE disks but it's been suggested to me that FUA commands cause all pending I/O to finish before they do -- that would suffice too.
-- thorpej