[NCLUG] scsi'd out

[R P Herrold]

On Wed, 28 Nov 2001, William Dan Terry wrote:

> I've never paid lots of attention to hardware, but want to add more disk
> space to a system. As it turns out, what was once SCSI now comes in many
> flavors and I don't know which end is up.
> 
> The specific is that I have an HP Visualize X550. It uses UW SCSI (68
> pin). Is this ultra different than ultra2 and ultra3? Or is ultra the old
> name for ultra2 or ultra3 (before they knew there'd be another one)? Are

I bought qty 2 of 9 G UW-SCSI New in Box from Hard Drive
Outlet, off ebay for $54 and $10 (each) shipping last week.

[This is horribly oversimplified - datasheets are your friend]

pinouts matter -- three major types still seen (excluding 
rarities like fiber)

SCSI-II -- looks an IDE end, but with 2 x 25 pins (rather than
	2 x 20) -- getting rarer due to low transfer rates
UW-SCSI -- 68 pin female connector on the drive -- W shaped
	polarized connector - market share fading
SCA (also called ultra2 and -3 by some vendors)
	-- 80 pin connector - still W shaped,  with a 
	center male projection in a female outer shell
*** DANGER WILL ROBINSON -- LV and HV -- Low Voltage and 
	High Voltage SCA variants exist  -- mixing will FRY 
	the opposite type controller and the drive -- Sun uses 
	HV -- others tend to LV
        -- expensive lesson -- check the manufacturer's site

This last (SCA) is commonly used in RAID arrays -- so the most
common sizes are $, 9, and 18 G variants;  in making a raid
array, it usually performs best in most a-pplications then the
drives are identical in size, spin rate, and usually
manufacturer, to allow spindle syncronization when striping
data.

-- Russ Herrold