Having some issues with a SCSI RAID array. Please help.

[CJan_NH]

First off, thanks for looking :)

I didn't know this tech forum existed until now-but I'm awfully glad it does.

I'm having performance issues with a SCSI RAID array that I just installed. The throughput of the array is less than a single IDE drive, so something obviously is going on that I can't put my finger on. The machine is a homebuilt with the following specs:

AMD Athlon XP 1800+
ECS K7s5a mainboard (SiS 735 chipset)
512MB Samsung PC2700 DDR RAM
ATI Radeon 64DDR VIVO
Creative Sound Blaster Live 5.1
Adaptec AAA-131U2 Ultra2 LVD SCSI RAID Controller
64MB EDO RAM buffer onboard card
(2x) 18.2GB Seagate Cheetah HDD ST118202LC (10k RPM)
Windows 2000 sp4

The array is running in RAID0. The device ID of the controller is 7, and the drives are 8 and 9.

I've updated all drivers, made sure PCI bus mastering was enabled in the BIOS and done everything else that I could think of. According to Seagate's diagnostic software the drives are running normally, and the controller does a full self diagnostic at POST.

Any ideas? Thank you in advance for your help!

[Ice Czar]

well for starters
Poor SCSI performance when using WinXP, or Win2k with SP3 or later (http://www.storagereview.com/php/tiki/tiki-index.php?page=XpScsiProblems)

arent those HDDs 80MB/s max (burst)

when you say less than an IDE
what is the throughput your getting and what was the IDE throughput your using as a comparision

[Snugglebear]

Those drives are over 6 years old.

[ambit]

And the card wasn't the best either.

[CJan_NH]

Thanks for your replies guys!

For benchmarking I used SiSoft Sandra and HDTach. The max burst speed was 34.5 MB/s.

For comparison the 40g Western Digital IDE drive in my other machine has a max burst speed of 88.2 MB/s.

There is a similiar Cheetah in my office PC that has comparable burst performance to the IDE drive above. The Cheetah at the office is a standalone drive though, not RAIDed.

I'll check the link that Ice posted. Thanks again.

Edited to add:

arent those HDDs 80MB/s max (burst)
Yes they are.

[Snugglebear]

Burst speed is how fast the drive reads off its buffer and is in no way indicative of performance in reality. Those drives are quite old and together will give you about the real performance of a modern 7200rpm ATA drive. I think that those drives max out at 40MB/s on the SCSI bus.

[CJan_NH]

I think that those drives max out at 40MB/s on the SCSI bus.
According to the specs they are capable of 80MB/s each with a seek time of 4.9ms, or is that something different?

My PC at work uses the exact same Seagate drive in a non RAID configuration, and it has more than double the performance of this array. That's why I think something is wrong.

[Poop]

Perhaps the card is the limitation?

Are they SCA drives?? If you're using adapters, that additional interface change could be degrading performance slightly.

[CJan_NH]

Are they SCA drives?? If you're using adapters, that additional interface change could be degrading performance slightly.
They use an adapter that converts the 80pin drive connector to the 68pin connector that plugs into the controller. According to the documentation they are LVD capable but maybe you're right.

This has been frustrating for me because my level of knowledge isn't what it should be when it comes to computer hardware. Back when I was running IDE RAID with a Promise controller everything was pretty simple. Troubleshooting this has been kicking my butt.

[Poop]

It's no doubt that they are LVD capable, it's just the fact that you're changing interfaces. Generally it's better to have a 68-pin drive.

[Ice Czar]

Originally posted by CJan_NH
They use an adapter that converts the 80pin drive connector to the 68pin connector that plugs into the controller. According to the documentation they are LVD capable but maybe you're right.




example:
http://www.mplayerhq.hu/homepage/design6/news.html

"Anyway we still have a small problem: the disks have 80-pin (SCA) connectors, and the 80-to-68pin converters I could buy here don't work in LVD mode, thus limiting bandwith to 40Mb/sec (SE mode). It should be enough for our current needs, but if you have 2 pieces of spare LVD-capable 80/68 converters, don't hesitate to donate! :)

sounds awfully familiar ;)

[CJan_NH]

Guys, thank you very much for your assistance-the problem has been tracked down and fixed. Earlier today I had the side of the case removed and realized that one of the drives was much louder than the other. I drove to the office and grabbed a spare to replace it and sure enough the array absolutely screams now.

The bad drive appears to have been killing the performance of the whole thing.

Now I'm happy :)

I realize that this setup isn't exactly state of the art, but the mortgage company I work for just upgraded their servers so I got this equipment for free. It's quite a bit better than what I had before so I can't knock it.

[Ice Czar]

Free is always good :D