SCSI maddness............. Arrays 101

[jtroutma]

Can some one explain this to me?

I have an Adaptec AHA-2940U2W adapter in my system currently and have 4 Quantum Atlas IV 9.1Gb HDD + 1 Quantum Atlas V 9.1Gb HDD on the U2W chain. I also have a DVD, Burner, Standard CDROM, and Zip 100 drive on the Wide channel. I have a SOFTWARE RAID 0 stripe set on the 4 Atlas IV HDDs using Win2K with 64K stripes.

Using that configuration, I can get a maximum data throughput of over 62MBps. Now here is what is bugging the hell out of me.

I purchased an Adaptec AAA-131U2 hardware array adapter w/ a 64MB cache DIMM on it. I then reconfigured my whole system so that all 5 HDDs were in a single RAID 0 config w/ 64k stripes. I get into windows and test it with the cache enabled and I can only hit 47Mbps throughput ONLY if all the CDROMS are unpluged from the array adapter! Otherwise, I get only 42MBps throughput!!!!!


What the hell am I doing wrong?!?!?
Every thing I have ever read tells me that a hardware array adaper should easily be able to outperform a software solution hands down.

Please help out a fellow WC please....

[Brad]

what benchmarking program are you using? maybe it doesn't like scsi raid arrays too well.

try running some of the tests that storage review run, see what scores you get

[jtroutma]

the two tests that I was using was the benchmark utility included with SCSIreset (small program good for reseting you SCSI bus and diagnosing problems) and Nero.

I will have to look into what storage review uses however there was a noticeable speed difference between using the AHA-2940U2W and the AAA-131U2.

[Boltz]

4 Quantum Atlas IV 9.1Gb HDD + 1 Quantum Atlas V 9.1Gb HDD on the U2W chain. I also have a DVD, Burner, Standard CDROM, and Zip 100 drive on the Wide channel

maybe some more detail is required, but here is what i understand...

you have 4 atlas IV's on a 50 pin cable and 1 atlas IV 68pin UW with a ZIP on the UW aswell....

as for the CD-Rom's... are they all IDE??? (IDE CD-rom, IDE DVD, IDE burner)??


Now, If i have any mistakes please correct me as i am prety much guessing from little detail you gave...

If you have 50 pin atlas IV drives, then it explains the whole situation...

If you ran a benchmark on the UW drive alone it should be good, but if you benchmark them all in a raid, then that slows down the whole scsi bus to the speed of the 50 pin drives. which is like 20MB/s sync

If you give more details it would heelp... give specific details as to cable types, adaptors convertors termination etc... (dont forget external devices too.

[jtroutma]

Well you got some of it correct.

All HDD are on the 68pin channel and all the CDROMS and the ZIP are on the 50pn.

The U2W channel (68pin) is all running at 80MBs and the 50pin channel is running at 40MBs.

Originally, all the HDDs were setup on the array adapter for RAID 5 and then in RAID 0 with 64k stripes and then 4K stripes. I did several experiments with the array adapter before I threw in the towel and went back to the Host adapter. So right now I have the Atlas V as my boot and the other 4 Atlas IVs in RAID 0 software controlled by Win2k.

Any ideas?

BTW the 68pn channel is tertminated at one end by the adapters and the other by a plug terminator rated for U2 operation. The whole 68pn channel is also running in LVD mode. All but two of the Atlas IV are capable of 160MBs but the other two are only able to run up to 80MBs.

[Boltz]

I cant really say, only that it shouldnt be slow.

does your boot drive benchmark better than an array ?

only thing that would slow it down is those 2 80MB/s drives in an array

but it shouldnt be that slow. i cant think of anything else other than going through your setup and check the settings of every device etc...


Also, you usually want a SCSI controller on its own IRQ... Not shared with any other device in the hardware profile of windows.... If it is then that might be an issue, but im not sure.

[jtroutma]

Checked the IRQ possibility from the start, the controllers are using IRQ 15 all by themselves (IDE Controllers turned off in BIOS and disabled in Windows).
The two 80MB HDD shouldnt cause a problem because the channel is only rated for 80MBs so they should max out when the channel does.

I know this sounds weird and that is why I couldnt believe it when I finally got the whole thing setup and discovered that it was soo much slower!

BTW the boot drive by itself benches at 26MBs and all the others bench at 20-22MBs.

Guess it is just time to dig out my old TSID number and give Adaptec a call.......

Thanks for you help guys.