I had a minor duh moment this week. For years I’ve worked on servers, big and small with SCSI disks. I’m familiar with SCSI technology and the quirks it has. In recent weeks I had purchased an ultra 320 SCSI hard disk for my linux workstation and an Adaptec 29160 card to drive it. I got the card used with a 68 pin SCSI cable complete with terminator.
I installed all the bits and mirrored my IDE disk onto the SCSI disk, rebooted and everything worked. Just to ensure there were no issues I was looking over my dmseg output and noticed the disk was running at 40mb/sec! I spent an hour going over jumpers and driver settings trying to figure out why this disk was running only at 40mb/sec. Then I actually looked at the cable connecting the two and realized that the cable was a plain old 68 pin Ultra SCSI cable. Doh!
For the curious, the way you can tell an Ultra 160 or 320 cable from a regular SCSI cable is the wires on a U160/320 cable are in twisted pairs. They use the same shielding idea as UTP ethernet cable to maintain speed at long cable lengths. Anyway, I’ve located some cheap U320 cables on ebay and they should be here any day now. Then I’ll be running at U160 from the disk to the SCSI card anyway. It won’t make a big difference since I’m only running the one disk on the SCSI bus and the data rate from the platters to the bus is only 60MB/sec.
Now if only I could get my DDS4 drive working with the 29160 card I’d be happy.
Why did you go with a 29160 controller when you have purchased U320 drives? wouldn’t you want U320 controllers as well to maximize your data transfer speed, since you paid for U320 HD’s? and is there also a difference in U160 to u320 cables or are they just the same? Just curious, maybe I’m missing something here.Thanks.
-L
The maximum transfer from the platter to the I/O bus with even the fastest hard disks is 50-60 megabytes/second so the added speed of U320 is irrelevant unless you’re running enough spindles to saturate the bus (more than 3 disks). The added cost of a U320 adapter isn’t really necessary when it’s only driving one disk. That money would be better focused on memory or CPU.
Ultra 160 and ultra 320 cables are the same.
Thanks for the SCIS cable info! That info has helped me a lot!