Re: [parisc-linux] scsi problem on a scorpio (715)

[Grant Grundler <grundler@parisc-linux.org>]

On Wed, Jan 07, 2004 at 10:30:30PM -0400, Steve Bromwich wrote:
> Grant Grundler mentioned that "as of 5 years
> ago, HP-UX default was 8 for servers and 2 for workstations";

The drives shipped with workstations had "Write Cache Enable" (aka WCE)
turned on by default.  Not good if you really care about your data.
But Tag queue depth of 2 works great because the drive will immediately
report "success" until it's on-board cache was full.

>  as the 715
> is a workstation it might be worth trying setting tags to 2 and seeing
> what happens?

Unless performance is more important than strict correctness, I still
reccommend tag queue depth of 8 and disable "Write Cache" setting.
Reducing queue depth further typically only limits performance.

I suspect something else is wrong in Riccardo's case. But it wouldn't
hurt disable queue tags completely and see if that is at least stable.

root@debian:~# sginfo -c /dev/sda

Data from Caching Page
----------------------
Write Cache                        0
Read Cache                         1
Prefetch units                     0
Demand Read Retention Priority     0
Demand Write Retention Priority    0
Disable Pre-fetch Transfer Length  65535
Minimum Pre-fetch                  0
Maximum Pre-fetch                  65535
Maximum Pre-fetch Ceiling          65535

hth,
grant