Smart Array 30 Enclosure Question

[JohnWRuffo]

The following is quoted from the MSA30 Product Description:
"Only HP allows for all Ultra320 devices to be compatible with previous Ultra3 and Ultra2 devices so customers can mix and match components in the same storage enclosure or server. When Ultra2 devices, Ultra3 devices and Ultra320 devices are found on the same Ultra320 SCSI bus, each Ultra2 device will transfer data up to 80 MB/s, while each Ultra3 device will transfer data up to 160 MB/s, and each Ultra230 device will transfer data up to 320 MB/s.. "

Any HP Enginner want to explain how it can do this if the drives are mixed "on the same bus"?

[Christian Schwartz-Søre]

If you mix and match the drives the faster drives will wait for the slower drives. In reality transfer rates like 320MB/s and 160MB/s, are no way near the numbers you'll see in real life. Rule of thumb a disk is capable of roughly delivering 5-10MB/s - determined by number of spindles, raid level, rpm, and block size.
Therefore in order to saturate a 320MB/s bus, you would need a lot of spindles.

My point is, don't focus too much on the available bandwith, cause a drives performance is no where near that limit.

Regards
Christian.

[JohnWRuffo]

I agree... but making a statement that the enclosure will allow U320 drives to transmit their data at 320 and if you stick a Ultra3 drive "on the same bus" that the enclosure will allow it to run a diferent protocol independently of the rest of the bus just seems very far fetched! I was always under the impression that if you place U320 and Ultra3 drives on the dame bus, the common protocol (Ultra3) would be forced. Thus, you could only transmit at Ultra3. This box claims to be a "break from the norm"!
It does not say anywhere in the documentation that "each drive" is on a separate bus or that it has or will act like it is some kind of managed network switch.