Date: Mon, 16 Jan 2006 07:36:52 -0500 From: insightinmind <[EMAIL PROTECTED]>
Using QuickBench, I'm comparing an ATA100 drive using a Sonnet Trio PCI (IDE133) controller and a SCA SCSI drive using an ATTO PSC SCSI PCI controller on a 50MHz bus computer, I find the ATA functions at 19-20 MB/sec and the SCSI at 22-23 MB/sec (Sequential R/W speeds).
Most likely your drives are the limiting factor. With very fast drives in a RAID, one can get up to 70 MB/s or so on those old machines. But even the most modern drives don't deliver much over 40 MB/s singly. And their speed drops off rapidly as the model of the drive gets older.
The speeds above are the actual performance the drive can deliver, which has little to nothing to do with the speed rating of the interface electronics.
Just because the drive interface (SCSI or IDE) is rated for 40 or 66 or 133 MB/s, doesn't mean that the platters on the drive sling data at that rate. A few years ago, top speed for a drive was 20 MB/s. Around 2000 top speed was only a little better than 12 MB/s.
For example, around 1994 the first Barracuda drives from Seagate came out. The ST32550W was a Fast & Wide SCSI drive rated for 20 MB/s (interface speed) but they can't deliver better than about 6 MB/s from the platters.
IBM drives have both an interface speed rating and a media speed rating which was considerably more honest. At least they did before they sold off to Hitachi.
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