Date: Mon, 13 Dec 1999 00:32:46 -0800 From: Mike Smith <msmith@freebsd.org> To: "Oliver Blasnik" <ob@omnilink.net> Cc: "Justin T. Gibbs" <gibbs@narnia.plutotech.com>, freebsd-scsi@FreeBSD.ORG Subject: Re: Again: CRD-Raid-Controller and FreeBSD 3.x Message-ID: <199912130832.AAA06120@mass.cdrom.com> In-Reply-To: Your message of "Mon, 13 Dec 1999 09:19:25 %2B0100." <00e201bf4542$c84a8bf0$c20effd4@jav.net>
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> > I just checked out the datasheet-pdf of that 5440 at cmd.com. They write
> > something about 32 commands-cache per host.
>
> Thinking about this... 32 commands per host... Hum... As far as CRD's show their
> logical partitions in a per-lun-basis, you could have e.g. 3 independend
> partitions, each with a 10,6 (*g*) commands-cache...
> Ough :( That dynamically things aren't good....
>
> I'll setup a max of 4 in cam_xpt.c and check it out. Possibly a recommended
> patch to cam_xpt.c would be to setup this, as far freebsd only supports 8 lun's
> by default (afair?). Any chances to get that into 3.4R? Justin? :)
No. FreeBSD starts assuming that a drive will handle 64 tags, but it
expects that the drive will correctly report a queue-full condition so
that it can dynamically adjust this number downwards.
If the problem in this case is that the CMD unit is accepting a tagged
command and then simply throwing it away, that's a bug in the CMD
firmware.
> Actual added this to cam_xpt.c:
> {
> /* Broken tagged queuing drive, 32 tqs per host */
> /* changed 12/12/1999 oliver blasnik fixno2 */
> { T_DIRECT, SIP_MEDIA_FIXED, "CMD TECH","CRD*","*" },
> /*quirks*/0, /*mintags*/0, /*maxtags*/ 4
> },
This may solve the "problem", but it will substantially degrade
performance in the case where there's only one array on the controller.
<shameless plug>
You might want to consider using a PCI:SCSI RAID controller like a Mylex
DAC960 or AMI MegaRAID. The host:cache bandwidth is _much_ better on
these units, and they typically offer all of the features of the external
units at a lower price.
</shameless plug>
--
\\ Give a man a fish, and you feed him for a day. \\ Mike Smith
\\ Tell him he should learn how to fish himself, \\ msmith@freebsd.org
\\ and he'll hate you for a lifetime. \\ msmith@cdrom.com
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