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SCSI data transfer problem

C

Chucu

Senior member
Ok here is what I have:
a western digital 9.15GB 10,000RPM ultra2 LVD HD on a ASUS CUV4X-DLS Motherboard.
The problem is that I am only getting 40MB/sec max data transfer on the drive according to the onboard SCSI utility. Also when I run SiSoft the drive performs MUCH slower then an ATA66 7200RPM drive. Any words of wisdom? I am new to SCSI.
Thanks
Chucu
 
Your transfer rate with an ultra2 drive doesn't sound out of line to me. I tested my ultra2 drive (before I sold it) against my ATA-100 7200 RPM drive and got similar max data transfer results; however, the access time on the ultra2 was tremendously faster than the ata-100.
 
Not surprising.

The U2 speed of 80MB/Sec is for the whole chain. It doesn't necessarily mean that one drive can supply the entire chain's speed. This is why SCSI is much more appropriate in multi-drive situations. If you have less than three drives, keep it IDE.
 
I have heard...(conventional wisdom) that the SiSoft HD benchmarks are highly unreliable...most people use HDTach, except for those of us on the NT platform, where's it's not free. 🙁

--Woodie
 

Sounds to me like your cable might be an SE (Single-Ended) cable - SE SCSI cable only can go as high as 40 MB/s (that is Ultra Wide).
In order to use Ultra 2 (Wide 80 MB/s or Narrow 40 MB/s) you have to use an LVD (Low Voltage Differential) SCSI cable.

That's most commonly the problem with the symptoms you've described. 😀.
 
An ultra2wide device has a (theoretical) max transfere rate of 80MB/sec.

On a hard drive, you will approach this figure only as long as the data being transfered from the hard drive is located in the drive's cache memory. This will happen when you repeatedly read a file(s) that is smaller than the drive's cache. If the data is not in the drive's cache, then the data has to come off of the disk platters which results in transfere rates more like the 40MB/sec you are seeing. If a lot of drive head movement is required to get the data, then the transfere rate is much less than that.

Paul
 
Dont worry about the scroes against other drives especialy against IDE/UltraATA, You will never win because most of those are hypothetical, you need to find someone that has almost simulare setups to get RT benchmarks. eg I have a freind with a Ath xp1500 with Ultra133 drives and has a hard time beating the sandra benchmarks for the DMA33 but in reality we know its alot better.
In the older sandras I could beat there scores with my adaptec 3940uw w/UW drive on a K6-550 system but the newer sandra I cant come close using a Adaptec 29160 with a Qantum 10k LVD on that same system.
In sandra my scores with it claiming Windows cache off but claiming buffered (go figure)
buffered reads 62
seq reads 18
buffered writes 10
seq writes 17
access time 6ms
with Windows cache used only thing changed was
buff writes 55
access time went to 2ms (I dont belive this at all)

In the older sandras I was getting buffered and cached scores in the 250+megs so things have changed but I dont know what they are testing spacificly anymore wether its what windows sees or the hardware itself.
I would suspect your HD is working right with that score.
Make sure you are using a Ultra2.U160 cable not just UW/SE, The extra windings do make a difference.

Comment, You cant use SE cables on Ultra2 and LVD drives without the external terminator, Most (90%) of Ultra2 and LVD do not support internal termination and some U2/LVD drives will not work with a SE cable period.

I love my scsi.
 
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