Re: failed command: WRITE FPDMA QUEUED with Samsung 860 EVO

[Sitsofe Wheeler <sitsofe@gmail.com>]

On Mon, 7 Jan 2019 at 08:46, Hannes Reinecke <hare@suse.de> wrote:
>
> On 1/7/19 8:41 AM, Sitsofe Wheeler wrote:
> > On Mon, 7 Jan 2019 at 07:17, Hannes Reinecke <hare@suse.de> wrote:
> >>
> >> On 1/4/19 8:33 AM, Sitsofe Wheeler wrote:
> >>> Blimey Laurence - you're really pushing the boat out on this one!
> >>>
> >> [ .. ]
> >>> I've yet to attach the disk directly to the mobo. It's a bit fiddly as
> >>> the most accessible port is meant for the DVD drive and I think it's
> >>> speed is slower than the others.
> >>>
> >>> The speed of the ATA ports is lower than you might expect (this
> >>> machine is fairly old):
> >>>
> >> [ .. ]
> >>> [    3.242623] ata2.00: FORCE: horkage modified (noncq)
> >>> [    3.242683] ata2.00: supports DRM functions and may not be fully accessible
> >>> [    3.242686] ata2.00: ATA-11: Samsung SSD 860 EVO 500GB, RVT01B6Q,
> >>> max UDMA/133
> >>> [    3.242689] ata2.00: 976773168 sectors, multi 1: LBA48 NCQ (not used)
> >>> [    3.245518] ata2.00: supports DRM functions and may not be fully accessible
> >>> [    3.247611] ata2.00: configured for UDMA/133
> >>
> >> 'slower' is an understatement.
> >
> > Are you surprised that there would be such a dramatic difference in
> > the speeds between the two SSDs (Samsung 860 EVO, Crucial MX500) on
> > that particular workload in that same machine?
> >
> Not at all.

Fair enough :-) My understanding is that both SSDs (when unloaded and
mostly empty etc) would be far faster than what this particular
machine could do but I stand corrected.

> >> That adapter can't do NCQ, hence 'WRITE FPDMA QUEUED' (which _is_ an NCQ
> >> command) will never be issued.
> >> So I'd be _very_ surprised if you still see this problem there ...
> >
> > I'm curious, why would using the libata.force=2.00:noncq kernel
> > command line (only mentioned in my very first mail) make using that
> > drive more stable if the adapter could never accept that command
> > anyway? Shouldn't the sending of that command have been disabled if
> > anything along the way can't actually accept it?
> >
> 'WRITE FPDMA QUEUED' will ever be issued if the drive _and_ adapter can
> do NCQ. As this is the offending command it's not surprising that
> switching off NCQ (and hence the use of that command) will make the
> machine more stable.
>
> Although I'd be curious about the 'more' bit in 'more stable'.
> I would have thought that the machine would be stable after disabling
> NCQ; do you still see issues after disabling NCQ?

I was inaccurate when I said "more": it has been totally stable since
disabling NCQ on that port.

> As for the NCQ issues: it might be that the adapter has issues with NCQ
> (quite some older adapters do).
> It might also be a problem with the _previous_ command which failed; can
> you enable libata tracing to figure out the command flow?

OK I'll see if I can get around to this one tomorrow.

Cheers!

-- 
Sitsofe | http://sucs.org/~sits/