SCSI Perfomance..

[CCrunnernb]

I have to Quantum Atlas 10K II SCSI hard drives.. there U160

Now when i run HDTach it say random access speed is 7.8 ms

and my read burst speed is on 80mb/s and my cpu init. is 7.0%

The specs say that the seek times should be about 5 and lower...

Is there something im missing? The card is an Adaptec 7899, I also have a 64bit raid card with 64mb SDRAM onboard.. even though the drives are diffrent one is a 9gb and the other a 18gb could I still use the raid card and benefit from the ram?

Thanks!

 

[Pariah]

Is there something im missing?

Yes, seek and access are not the same thing. You have to add average latency (3ms for 10k drive) to average seek to get average access. 3 + 5 = 8, which is basically what HDTach reported to you. Manufacturers often quote "optimistic" seek times as well which drives don't quite live up to in real world tests.

 

[ledzepp98]

i can only answer the part about the access time... basically, access time is the seek time plus the rotational latency (which is about 2ms for a 10k drive, 3ms for a 10k drive, and 4ms for a 7.2k drive). the manufacturer specs list the seek time, add the rotational latency and you have the access time (in your case, ~4.8ms seek + 3ms latency = 7.8ms access time).
That is a simple overall view (anyone please correct me if i have made a mistake...)


edit: looks like i was right, but not fast enough

 

[CCrunnernb]

I would like to use this raid card, how to I combine the two drives.. which array would I use?

 

[StraightPipe]

if you combine the 9GB and 18 GB then you will lose half of the larger drive. anything that isn't matched will not be used in raid. so you'll actually get 9+ 9=18 so it's kinda waist of time, since one of your drives already is 18. you might try JBOD so you'll get 27GB. unless your willing to throw away half the larger drive for performance improvement.