SCSI slow?

[Maz28]

Hi guys, I have a question.

I am building a workstation with a combination of: PATA drives, SATA II drives, and SCSI Ultra-320.

Now, when I tested the Read / Write speed I obtained the following results in MB/sec:

PATA (IDE).................48.........43..........OK
SATA.........................62.........54..........OK
SCSI..........................28.........23..........VERY POOR

I thought there was something wrong with my onboard SCSI controller but when I tested the SCSI drives through an old 2940 Adaptec card (that provides at least 40 MB/s) I got exactly the same:

................................28.........23........It must be the drives, I thought.

But even though they are not the latest, I never thought there was ever a SCSI so slow!
Or was there? :?:

Well, that is my question. I have never had reason to test drive speeds before so I am totally unaware of the performance of these drives nor I can find them on the net. I don’t want to blame the mobo yet, so I would appreciate any suggestions.

SCSI DRIVES:

Seagate Cheetah....ST19101WC.............9 GB....Hot-swap
Compaq................BD018122C9...........18.2 GB....Hot-swap
Quantum...............Atlas 10K 3.5 series...9.1 GB

Also, the two hot-swap drives don’t work at all unless an old 50-pin CD cutter is added at the end of the array.

I guessed that may be due to the 80 to 68-pin adapter possibly being too old and thus incompatible with U320. Possible?

And if so, why would they work in conjunction with the 50-pin SCSI device and not alone?
I always added a terminator in all my tests.

I thank you all for your time.

Maz

 

[TabrisDarkPeace]

Density of data:

The outside zones on 9-18 GB at 10-15 Krpm SCSI drives spins fast, but doesn't transfer all that much data. They will seek quickly and that is about it.

You are meant to run 4+ of them in RAID-0/5/6 to see data transfer rates rise.

The outside zone (and even mid zones) on a 80 GB HDD at only 7,200 rpm will be able to transfer data far faster, although the seek time will not be as nice. (Platters are actually larger in diameter, so the outside edge may spin at a speed on par with a 15 Krpm drive, while having a higher density of data per revolution).

If you only partition 1/3rd of the 80 GB at 7,200 rpm it will actually outperform the SCSI HDDs you have in both DTR and likely in seek times aswell.

If DTR (Data Transfer Rate) is your main concern, just get a bunch of 160 - 400 GB (say 300 GB) HDDs at 7200 rpm, and run them in RAID-0/5 (or RAID-6 if using heaps).

A more balanced solution would be some 147 GB (say 4 in RAID-0/5) at 10,000 rpm... be them SCSI or SATA, or even ATA100. You'll get decent seek times, and *far* higher Data Transfer Rates, just because they are more dense.

Think about how much data can be transferred in 1 revolution, the larger the capacity, the more data can be read / write. High 'rpm' is just for low seek times, which only help if more than 8 people are using the HDD at once.