Very Slow Array (SCSI)

[Wes Dunstan]

I am having a problem with a SCSI array (4-4.3GB Compaq Drives 7200rpm) using an adaptec controller...

Problem is that when I do a benchmark on the individual drives, I am comming up with just under 7000kps transfer rate, whereas my IDE 5400rpm 30GB drive is pumping out 18000kps... It's my impression that a 7200rpm drive would beat the pants off my IDE, and on top of that it is Ultra-Wide SCSI... When I set the array up as a level 0 RAID, I can achieve about 17000kbs, which is still poor compared to my IDE.

If anyone else has had this problem and has managed to solve it, I would appreciate a hint or two. I have tried everything I can think of, including trying it out on my server computer but I get the same speeds.

Please help me!

- Wes

[Greg Carlson]

Wes,

Here is a document that will show you Why you see such a difference.. http://www.cs.virginia.edu/~bsw9d/papers/ide_scsi.pdf

The hdds in this study are 30GB IDE hdds at 7200RPM compared to some 36GB 10k rpm SCSI hdds. Also your IDE hdd is probably an ATA-100 or 66 which is running at 66/100 MB/s compared to those old SCSI hdds running 40MB/s.

Ciao,
Greg

[Marino Meloni_1]

hi

another info:
>>When I set the array up as a level 0 RAID, I can achieve about 17000kbs

When you select a redundand raid level, the transfer rate is lower than in a raid 0 because the controller have to write two time the data and one time these data have to be compressed, also other task are performed by raid controller onthe hdd, that is because a raid level 5 will be slower than a raid level O.

bye

marino