[EMAIL PROTECTED] wrote...
> On Thu, 6 May 1999, Kenneth D. Merry wrote:
>
> > The LXY4 firmware (and earlier firmware versions) on Quantum Atlas II's is
> > known to be buggy. If you have enough I/O going on the drive and on
> > the SCSI bus, the drive will go "out to lunch" and will require either a
> > BDR or a bus reset to wake it up.
> >
> > The LYK8 firmware is buggy as well, at least with respect to tagged
> > queueing, but at least the drive won't hang with that firmware.
>
> The funny thing is, when I asked about firmware upgrades, an engineer at
> Quantum told me there were no known TQ related bugs in LXY4, but suggested
> I could try LYK8.
Well, the major bug in LXY4 isn't really related to tagged queueing
specifically. It's that the drive locks up under load. But it's easiest
to reach that sort of load by enabling tagged queueing.
> > The reason your system was more stable with tagged queueing disabled is
> > probably because you drastically reduced the I/O load on your drive, but
> > you probably also reduced the random I/O capability of your striped drives.
>
> Yeah. It definitely was slower with TQ disabled, but at least it worked.
> I'm running now with write caching on the drives disabled and a queue
> depth of 8 per drive. So far, it seems stable and performs reasonably.
>
> What bugs have you found in LYK8? I'd like to figure out if it's worth
> trying to upgrade or if I'm better off just leaving things as is now that
> they appear to work.
Well, the main bug in LYK8 is the same bug that most every high-end Quantum
drive has nowadays. It continually returns Queue Full under high load, even
when there are very few transactions queued to the drive.
We "fixed" it in FreeBSD by setting a lower bound on the number of
transaction slots (24) for Atlas II and III drives. Without that, we
would automatically reduce the number of slots (or queue depth) to the
system-wide minimum for devices with tagged queueing enabled (2
transactions).
I think you would certainly be better off upgrading to LYK8, since it won't
hang like LXY4 does.
Ken
--
Kenneth Merry
[EMAIL PROTECTED]
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