Ultra 160 vs Ultra 320 SCSI Hard Disk

Posted on 2008-06-18
Last Modified: 2011-10-19
I have an old server, an IBM xSeries 360, which according to the documentation, can only support up to Ultra160 disks.
I'm having a hard time finding Ultra160 disk, while there are a lot of Ultra320 on the market.
I wonder if an Ultra320 disk will still work in this server.

I was thinking if getting a few of these:

For my experience in IDE and SATA disks, when you get a disk with newer and faster technology in an old equipment, the only problem is that the full speed/transfer is not achieved, however, they still work. But in SCSI disks I have no idea.

I'm attaching the IBM xSeries 360 Specs Sheet.

Question by:fischermx
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LVL 10

Expert Comment

ID: 21817199
It would work. Performance would be terrible and the drives would fail much sooner.

I would not recommend doing this.

Author Comment

ID: 21817238
Really????? :(
LVL 10

Expert Comment

ID: 21817272
The drives would have to "step down" in order to run at the slower speed, they are not designed to do this and would not do it well. In addition the SCSI controller may not even recognize the drives properly.

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Expert Comment

ID: 21817289
ypu have to get the apropiate cables to connect the 320 to 160

Author Comment

ID: 21817316
But they are all 80pins connectors... why different cables?

Actually, they don't even need cables, they are hot pluggable!

LVL 10

Expert Comment

ID: 21817349
Let me be clear, this will end badly for you and I don't recommend pursuing this route.

I also believe that your SCSI controller in this system may not detect the drives or be able to communicate with them.
LVL 34

Assisted Solution

jamietoner earned 200 total points
ID: 21817628
They will work fine. These statements "they are not designed to do this and would not do it well" WRONG and "Performance would be terrible and the drives would fail much sooner" also WRONG. U320 drives are backwards compatible and should work without issue on a U160 controller, the performance will be the same as a U160 drive and will not affect the drive's MTBF.

Author Comment

ID: 21817660

Actually, I've just found another reference right here in EE, that agrees with you:

Also, in this website:

Someone here, made the same question:

And here:

LVL 70

Expert Comment

ID: 21817828
The drives will work fine !!   The performance of the drives is NOT impacted at all --> they still rotate at the same speed; the seek times aren't any different; etc.   The ONLY difference is that the interface speed is different (Ultra 160 vs Ultra 320).   ... and it certainly has NO impact on the reliability of the drives !! [r.e. "... the drives would fail much sooner ..."].

LVL 70

Accepted Solution

garycase earned 300 total points
ID: 21817850
... in fact, unless you're using an array which could support a sustained transfer rate higher than Ultra 160 speeds, the ONLY time there would be any difference in performance (compared to an Ultra 320 controller) will be in transfers to/from the drive's buffers => a very low % of disk operations.

Bottom line:  Buy the disks you listed.  They'll work just fine :-)

LVL 95

Expert Comment

by:Lee W, MVP
ID: 21818722
I complete agree - these drives should be just fine.... I have no idea what 0xSaPx0 is talking about who where he's getting his information.

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