Re: SCSI vs SATA considerations

[Douglas Gilbert <dougg@torque.net>]

Mogens Valentin wrote:
> Guy wrote:
> 
>>Check the jumpers on the disk.  Most have a force SE jumper, that would
>>limit you to 40M/s.
>>Also, anything else on the SCSI bus?  If so, if 1 device is SE the bus
>>must be SE, which would limit you to 40M/s.
> 
> 
> No other devices on the scsi bus.
> The SE jumper is not installed. Tried with/without - once had an older
> IBM scsi disk where the docs had the definition on one pin reverted :-
> I had it jumpered as ID2; making it ID0, for some reason it properly
> negotiates as a 160 device, at 80MHz, of cause.
> I still get only 34.4 MB/s, though (misspelled the speed in first post).
> Tried forcing 80MB/s, disabling domain validation, and forcing
> termination on the 29160, no change.
> 
> Been thinking if IBM at some point sold some DDYS's as pure UW 40MB/s
> disks, to satisfy the market...
> 
> Out of ideas, except flashing the controller. Latest BIOS should do some
> BIOS optimizations and device order stuff, whatever that means.

Mogens,
Perhaps you could try sg_rbuf in the sg3_utils package (see
http://www.torque.net/sg ). sg_rbuf uses the READ BUFFER
SCSI command and on most disks (e.g. recent seagate and
fujitsu) sources data out of the disk cache quickly. The best
figure that I have seen is about 110 MB/sec on a U160 bus when
the streaming performance of the disk was about half that figure.

IBM transferred their disk business to Hitachi (joint venture?)
a few years back.

BTW recent press releases from maxtor and fujitsu claim 100
MB/sec streaming performance on the U320 bus for
(soon to be released) 15k rpm disks.

Doug Gilbert