Why is my IDE drive faster than my SCSI drive???

[XxMaCaBrExX]

I just installed my Adaptec AHA-2940UW card and connected a 4gig SCSI HD. Now, I looked up the model of the drive, they are made by Fujustu, the M2954 is the model. These are supposed to be 7,200rpm with 36 MB/s buffer throughput. Now why in the hell am I getting a maximum read and write speed of 4,000kb/sec on this 7200rpm SCSI drive when my ATA66 5,400rpm IDE drive gets read/write speeds up to 21,000kb/sec???

[Icarus]

Don't want to start any SCSI vs. IDE fights here, but IDE is past the point where it is better then SCSI. SCSI still reigns supream in the server market because of their stability.

Your problem might be a bad setup for you SCSI drives. I don't know too much about SCSI but what kind of interface card is it using? I might be wrong but there are 4 or more levels for SCSI cards, 1=20MB 2=40MB 3=80MB 4=160MB. (I think that's how it goes...)

Looks like your I/O card is only a level 1 or 2, Just my observation, if I'm wrong may the SCSI Gods strike me down :p

[XxMaCaBrExX]

AHA-2940UW Technical Specifications (http://www.adaptec.com/worldwide/support/techspecs.html?sess=no&prodkey=AHA-2940UW&cat=%2fProduct%2fAHA-2940UW)

Data Transfer Rate 40 MByte/sec

[michaelk]

Do you have any other devices on the same chain?

f you have any 8 bit devices it is only 10mb/sec.

[ 17 June 2002: Message edited by: michaelk ]

[XxMaCaBrExX]

The 4gig drive is the only device connected to it.

[bastard23]

You should be getting faster rates, you won't get 21MB/s off of that drive. It's older, slower, and probably louder.

You can see the trasfer rate in linux. Run dmesg|less and look for the scsi info. I've got a narrow version of that card and I get around 10MB/s off of 4G seagate barracuda drives which should be similar to yours. Also, look at the internal transfer rate off of the disc, which usually means more than the buffer rate. Your drive is 15 MB/s of of the HDA. I don't know how fujitsu reports their rates, but it probably means something closer to 10 MB/s max over the bus.

You can change the speed of the scsi transfers in the Adaptec setup while you boot (Ctrl-A to get to setup.)

What are you using to test the transfer rates? I've always used hdparm.

Good luck,
chris

[XxMaCaBrExX]

Timing buffer-cache reads: 128 MB in 0.72 seconds =177.78 MB/sec
Timing buffered disk reads: 64 MB in 7.08 seconds = 9.04 MB/sec


I get this from running "hdparm -Tt /dev/sda". My other measurements were from using the HD Benchmark tool from mindbeat.com (in Winblows eXtra Poop

[thedexman]

Your SCSI drive is pretty old, that's why it's benchmarking so poorly. Almost any IDE drive made in the last 3-4 years is faster than that Fujitsu. IDE drives are faster than most SCSI drives in single-user setups these days. Right now, you won't really see better performance on a PC out of SCSI unless you have a more recent 10,000 or 15,000 RPM drive.

[ 18 June 2002: Message edited by: thedexman ]

[bastard23]

XxMaCaBrExX,
9 MB/s sounds about right. You probably shouldn't expect much more than that. Just check that the kernel reports the drive running at 40MB/s (20 Mhz) instead of 20.000MB/s transfers (10Mhz.)

chris