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Help on SCSI RAID

C

cvlegion

Senior member
I am new to SCSI and SCSI RAID. However, I just got a PERC 3 (AMI Elite 1600) SCSI RAID card and 2 Seagate Cheetah ST318405LW's. I put them in my computer and they are working like a dream. However, I do not think that I am getting all I can get out of this setup. I ran a Winbench Disk Transfer test and I am getting a flat line basically at 52Mbps. Now of course this means a bottleneck since each of these drives have something like a 40Mbps beginning and a 25Mbps end transfer rate so I would expect a sloped line starting somewhere closer to 80Mbps and ending somewhere around 50Mbps. So I am wondering is it Winbench (I really doubt it) and if it is could you recommend a better set of benches to test my drives. Is it my settings on my card? I have it set at RAID 0, Write Thru, Cached I/O and I think 64K stripes. I will look into that a little later and modify this post. I have a 64Mb DIMM on board but no battery pack. First time I installed OS I did Write Back, Direct I/O and it had exactly the same result. Or could it be my setup in anyway. I have an Epox 8KTA3+ w/ 1.4GHz T-bird. Of course this means that I am running the card on a 33MHz, 32bit PCI slot even though it has a 66MHz, 64 bit PCI plug. I am running Windows 2000. I am including the link to my system specs so if you are able to extrapolate any other potential problems. Another thing that I noticed is somewhere in between the time I first installed Windows 2000 and when I ran all the updates on the Microsoft site, there is a slightly annoying pause on startup. It last for two seconds where I cannot open up the Start Button. Of course both of these I can live with because once my computer is on, then there are absolutely no problems. Also I can live with a 50Mbps tranfer rate 😀, however when I dropped $900 on this I would like as much out of it as possible. I appreciate any and all help.

System Specs
 
That sounds like a nice setup. Congrats.

<< I ran a Winbench Disk Transfer test and I am getting a flat line basically at 52Mbps. Now of course this means a bottleneck since each of these drives have something like a 40Mbps beginning and a 25Mbps end transfer rate so I would expect a sloped line starting somewhere closer to 80Mbps and ending somewhere around 50Mbps. So I am wondering is it Winbench (I really doubt it) and if it is could you recommend a better set of benches to test my drives. Is it my settings on my card? >>

Your card is the limitation and most likely your settings will not get you much better results. The flat line indicates a bottle neck, as you noticed. In this case it's the RAID card itself, not the drives. Or more specifically, the i960 chip on the card.

I looked up the specs on your card and it uses an i960 controller at 100MHz. Most likely that chip is only capable of about 52MB/s.

This is a very common disappointment for these types of RAID cards. They work differently than say, a Promise controller, where you would actually get almost double the transfer rate.

Where these cards really shine is on something like random transfer rates. In comparison to an IDE RAID, your card will smoke it in that area. SCSI RAID cards are usually targeted towards I/O per second, not necessarily total sustained transfer rate.

<< I have it set at RAID 0, Write Thru, Cached I/O and I think 64K stripes. >>

Sounds all good except you want to change the cache to write back for the most performance. This can be dangerous if you don't have a battery back up though. The card will store the data in RAM and will signal that the data was written to disk before the information has actually been written on the drives. If you loose power during this moment, your data will be lost.

So, I'd say your system is performing up to spec and I'd bet it's pretty &quot;snappy&quot;.

And, like I said, if you want to make yourself feel better, compare random scores. Of run the other disk tests on Winbench 99, like Disk Winmark, and compare those to a single drive score from Storage Review.

Don't run HDTach. That will really disappoint you.

If you really can't live with those scores I'd suggest a RAID card with a faster controller chip. My Mylex card runs at 233MHz and the transfer rate maxes out at about 95MB/s even though my drives are capable of more.
 
Thank you for your help, I will look into a new card later; I know I won'd lose money if I sell it back. I had been thinking about getting a Mylex Extremeraid card (if I can find it at a good price), so I will think about that.
 
1100, just read about my rig in my sig. 🙂

I've considered upgrading to the 2000 but I can't seem to find one with 3 internal channels and I'd have a hard time justifying the money for something so similar to what I have. I think the only thing I would gain is the U160 interface. I only have one drive on each channel so I think the 80MB/s Ultra2 limit of the 1100 is fine for me.
 
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