Date: Sun, 04 Feb 2001 18:10:30 -0800 From: Mike Smith <msmith@freebsd.org> To: Tom Samplonius <tom@sdf.com> Cc: freebsd-scsi@freebsd.org Subject: Re: Tags and the mly driver Message-ID: <200102050210.f152AUc01543@mass.dis.org> In-Reply-To: Your message of "Sun, 04 Feb 2001 12:41:49 PST." <Pine.BSF.4.05.10102041234140.11446-100000@misery.sdf.com>
next in thread | previous in thread | raw e-mail | index | archive | help
>
> According to camcontrol, SCSI disks attached via the mly driver are not
> using tagged command queuing by default.
>
> I've been investigating why the performance of the a Mylex AccelRAID 352
> (mly driver) was about 30 to 40% slower than an older Mylex AccelRAID 250
> (mlx driver). mly uses the CAM layer, and mlx does not. Performance was
> measured with postmark using 10,000 files, and 50,000 transactions.
>
> Anyhow, attempts to raise the number of tags via camcontrol via seems to
> work (camcontrol tags da0 -N 4), however shortly after increasing it to
> 16, the entire disk array hung.
>
> Are tags just unsupported on drivers that provide a virtualized SCSI
> interface like the mly driver? Or are there driver and/or hardware
> limitations that prevent them working?
I'm not entirely sure what the problem is here; it was my impression that
by returning PI_TAG_ABLE in hba_inquiry from XPT_PATH_INQ that tagged
command queueing would automatically be enabled.
As it stands, this is probably a vindication of my general preference not
to make RAID volumes look like SCSI disks - they don't typically behave
anything like them, and stupid things happen when you try.
Inre: your other message; the "AM completion for illegal slot" message
means that the controller returned a completion status indicator for a
command ID that was not actually in use.
I've recently fetched all my controllers back out of storage, so with any
luck, I'll be able to post a followup to this in a little while with a
better answer for you.
Regards,
Mike
--
... every activity meets with opposition, everyone who acts has his
rivals and unfortunately opponents also. But not because people want
to be opponents, rather because the tasks and relationships force
people to take different points of view. [Dr. Fritz Todt]
V I C T O R Y N O T V E N G E A N C E
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-scsi" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200102050210.f152AUc01543>