Sign in with
Sign up | Sign in
Your question

Help: 15000rpm SCSI disk writing at 12 mb/s.

Last response: in Storage
Share
July 18, 2007 2:23:43 PM

Hi, I have a new Dell precision 390 workstation to record images captured by a video camera through a National Instructment frame grabber. As we need really fast capture speed, we choose the best SCSI disk available at the time, and hope to achieve the best writing speed. However, the system was performing extremely poorly, only recording 9 frames per second. A test with .NET 2.0 Disk Benchmark II shows the problem: when use Windows (.NET) Disk Caching, the write speed of the hard disk dropped significantly with large block size. And at block size 2048, the speed is a ridiculous 12.257 Mb/Sec, which is the speed we got from our camera at the end (please see the screen shot below). I don’t understand why it is happening, I tried to add a normal SATA disk to the system, and the speed come out as 46mb/s at block size 2048, almost 4 times better than the SCSI.



I talked to Dell’s technical support for the last few days, we upgraded all the possible drivers and firmware but nothing changed. There was no error message from the Dell’s hardware diagnostic, in the end they gave up claiming that’s not their hardware problem and I am running out of options now. I would really appreciate anybody’s suggestion, just to give me a clue why is it happening and hopefully I can find a solution. Thank you very much indeed.

The system is a Dell 390 precision workstation, using Intel Core 2 Duo 2.4G processor, with 4.0 G DDR RAM. The hard disk is a 146GB(15000rpm) FUJITSU MAX3147RC SCSI Disk, without RAID.
July 18, 2007 3:22:48 PM

What SCSI controller? How is it connected, describe cable and what termination used, and where. I have AHA-2940U2W which benchmarks at 66Mb/s with a 10k rpm drive. Sounds like cable/termination problem.

Mike.
July 18, 2007 4:25:45 PM

Hi Mike. Thanks for the reply. The SCSI is using Dell SAS 5/iR Adaptor controller. I am not sure how is it connected though. But I don't think it's a cable problem, as it Bench Marked at 72 Mb/s with 256kb blocksize. The strange thing of the disk is it can certainly reach fast speed, but the writing speed drops so dramatically with large block size. As you can see from the screenshot. At block size 256kb, the speed is 72mb/s, at 512kb, it dropped to 15mb/s, and at block size 2048kb it is merely 12mb/s.

I am not an expert on hard disk, and I don't even understand fully what does block size mean in the test, but I know the frame grabber is certainly writing at around 12mb/s in the end. Is it normal? Thanks again!
Related resources
July 19, 2007 1:54:57 PM

Prozuzu said:
Hi Mike. Thanks for the reply. The SCSI is using Dell SAS 5/iR Adaptor controller. I am not sure how is it connected though. But I don't think it's a cable problem, as it Bench Marked at 72 Mb/s with 256kb blocksize. The strange thing of the disk is it can certainly reach fast speed, but the writing speed drops so dramatically with large block size. As you can see from the screenshot. At block size 256kb, the speed is 72mb/s, at 512kb, it dropped to 15mb/s, and at block size 2048kb it is merely 12mb/s.

I am not an expert on hard disk, and I don't even understand fully what does block size mean in the test, but I know the frame grabber is certainly writing at around 12mb/s in the end. Is it normal? Thanks again!


I have to question this disk benchmarking program you're using. While it's reporting these slow writes, it's also reporting ~ 800MB/sec reads, which is impossible on a single drive. Furthermore, these extremely large block sizes that it's working with (2 MB ?) are not realistic - virtually no application I know operates on the disk subsystem with gigantic block sizes like this.

Download the 2004.07.30 version of IOMeter, and run a workstation benchmark and/or 32K 100% writes test with exponentially cycling queue depths. (See the IOMeter documentation for how to do this) and report the results here.

I don't think anything's wrong with your drive.
a b G Storage
July 19, 2007 2:12:59 PM

Yeahhhhh....the numbers that program is spitting out don't make much sense.....
July 19, 2007 2:36:41 PM

Open device manager and check out SCSI controller. The HD you quote is SCSI, but the controller you mention is SATA! ID the make and model of the SCSI controller.

Mike.
July 19, 2007 6:52:34 PM

Thanks all for the reply. The SCSI controller is indeed Dell SAS 5/iR adapter controller, which is not a SATA controller.
I will aslo try to run the IOMeter SomeJoe777 recommended tomorrow, and let you guys know the result later.

The reason I used .net benchmark II as the measure is because so far, all the result it reports make sense for us. The system was purchased to record images from a Mikrotron video camera, through a National Instrument PCIe-1429 frame grabber. We soon found that the PC is recording the images at extremely slow speed (only around 9 fps, which is around 12 mb/s). I was informed by the technical support for the camera system that the camera is using 1024 or 2048 kb buffer size, so it matches the speed reported by the BenchMark program perfectly well. I also tried to add a SATA disk on the PC and test it with Benchmark program again, it reports 46 mb/s speed at large block size, which again, matches the performance of the camera (with the SATA disk, the frame grabber can record around 40 fps). By any means, the SCSI disk should perform 4 times worse than the SATA disk, so I really think there is something wrong with the system, but just couldn't figure out why is it happening.
February 8, 2008 5:44:18 PM

I am having the same issues with my scsi drive. I have been searching for a solution. I breifly read via google search that XP has an issue with SCSI drives. Some sort of indexing setting or something. I need to revisit.

Are you using XP?

Did you ever find a solution ?

!