Hi,

I have an old server with dual PII and SCSI, I think it is Ultra Wide SCSI, but I'm not sure about this. It is an IBM Pc Server 325, so if someone knows better what is inside it, please tell me.

The problem is that my SCSI drive seems too slow and I really don't know what could be done about it. Well, hdparm said the speed was a little more than 8MB/sec and this seems low as the driver informs be 40MB/s during boot.

hdparm -t -T /dev/sda

This is from dmesg:

As I have not any real specs for my machine it is difficult to know what the SCSI in use is and what the rest of the hardware is. Now I would like to know whether there is someone with more knowledge about this machine or how to "fix" the SCSI thing. Please help as I am quite new to SCSI and have tried to search the Internet for help in this matter, but without luck.

Thank you in advance!

Is there noone with knowledge about SCSI?

I would just want to know what the speed should be as I think it is too low. Please tell me what speeds you are experiencing with similar SCSI buses.

Thanks!

I have 2 SCSI computers, one is similar to yours. Here are my results if you're interested

Computer is a P2 333 MHz, AHA-2940UW (40MB/s bus)
# hdparm -t -T /dev/sda
/dev/sda:
Timing buffer-cache reads: 128 MB in 1.44 seconds = 88.89 MB/sec
Timing buffered disk reads: 64 MB in 2.93 seconds = 21.84 MB/sec

Computer is a 1.83GHz Athlon AHA-19160 (160MB/s bus)
# /sbin/hdparm -t -T /dev/sda
/dev/sda:
Timing buffer-cache reads: 1780 MB in 2.00 seconds = 890.00 MB/sec
Timing buffered disk reads: 204 MB in 3.01 seconds = 67.77 MB/sec

Thanks randyding for giving me at least something to start with. Well, the first thing that comes to my mind is why are you having so much better results than i have? This was exactly the thing I was suspecting all along.

Could it be so that the driver is the same for both of us - that's why it prints 40MB/s - but the bus is not the same?! Or is this totally impossible?

Any other ideas?

I wouldn't rule out software problems yet but there are some hardware problems that can cause poor performance. The 4 big ones that I've run accross in some of my systems has been
1. bad scsi cable or connector
2. improper bus termination
3. bad hard drive
4. bad controller card
I've sometimes seen degraded performance just before a drive failure. Most of the time you start to hear unusual sounds of head movement on the drive.

I personally have not seen the diagnostic software for linux, but there is some adaptec software that does diagnostics on others where they print out scsi bus and drive error logs and codes.

You may take a look at the SCSI bios screen, you hit some key on bootup to get into it. Depending on the adaptec card there usually is some diagnostic programs that can be run from there too.

You may also check that your hardware really is the speed you think it is. SCSI drives come in speeds from 5 to 320 MB/s, and the bus speed is going to negotiate to the slowest device on the bus. I'd also double check that all your drives are the same bus, like you don't want to mix LVD and Single Ended drives (both have the same 68 pin connector) and that you have the right controller type, like my 2940UW is single ended only and some newer LVD don't work for some reason... they are usually backward compatable but I have a Maxtor that shows problems (runs very slow) with that controller.

If all else fails, try Adaptec tech support. I've called them a couple times for various things and they've always been helpful.

Thank you very much for the answer!

So, you mean that if I have the SCSI CD-ROM connected to the same cable and this has a speed of 10MB/s the speed of the SCSI harddrive will be 10MB/s even if it says 40MB/s when it boots? If this is the case it can easily be checked when I get home from work.

Well kind of, if your SCSI cd-rom(s) are like mine then they have the 50 pin connector. Which is single ended 8 bit ultra SCSI (20MB/s).
I don't know your exact setup, but the 40MB/s scsi bus is ultra-wide and it usually has the 68 pin connector on the drives. So they can't be plugged into the same SCSI cable unless you are running the ultra-wide drive on the ultra bus using a scsi adaptor.
Normally, the adaptec controllers have 2 different SCSI busses and two different connectors, one is ultra scsi for cdrom's, etc, and a different one that is faster for hard drives. They are usually on separate cables but don't necessarily have to be, depending on your card and the cables/adapters you are using.
You probably should take it all apart and write down what you have and how its all connected to troubleshoot it more. The adaptec web site has lots of good scsi diagrams that explain everything and what's compatible with what. I've got a lot of those PDF files and reference them everytime I have to work on stuff. It helps a lot to know the part numbers and get the data sheets for each part in your system too.