On Fri, Sep 23, 2016 at 01:02:26PM +0000, paul.kon...@dell.com wrote: > > > On Sep 23, 2016, at 5:49 AM, Edgar Fu?? <e...@math.uni-bonn.de> wrote: > > > >> The whole point of tagged queueing is to let you *not* set [the write > >> cache] bit in the mode pages and still get good performance. > > I don't get that. My understanding was that TCQ allowed the drive to > > re-order > > commands within the bounds described by the tags. With the write cache > > disabled, all write commands must hit stable storage before being reported > > completed. So what's the point of tagging with cacheing disabled? > > I'm not sure. But I have the impression that in the real world tagging is > rarely, if ever, used.
I'm not sure what you mean. Do you mean that tagging is rarely, if ever, used _to establish write barriers_, or do you mean that tagging is rarely, if ever used, period? If the latter, you're way, way wrong. Thor