Re: separate hard drive for scratch disks for two different programs?

According to Floyd L. Davidson <floyd@xxxxxxxxxx>:

[ ... ]

It's worse than it looks too. While the 300GB SCSI
measures out at a higher speed than the 750GB SATA
drive, that happens only when testing the outer
cylinders. When the two devices have 270GB of data on
them, not only does the SATA drive still have that much
more (while the SCSI drive is full), the SATA drive is
much faster using the middle cylinders than the SCSI
drive is using the inner most cylinders.

This is a function of the way the OS deals with the disk, If it
insists on seeking to the early tracks frequently, yes. If it keeps the
heads fairly localized, this is not a problem. This would argue for not
putting the swap partition (unix) or the swapfile (Windows) on the same
disk where your heavy data activity is located.

And the same argument can be used against the SATA drives, if
they happen to get near full too. And there, you don't have the option
of sharing the load between multiple drives, because you are wanting the
maximum capacity per drive.

That means if the actual need is for anything more than
perhaps half of the storage space available on the SCSI
drive, the SATA drive will not only be 6:1 less
expensive, but have a higher performance in *all* ways.

I don't accept that if a good OS is used which keeps seeks
localized.

And -- if you are using two SCSI disks in place of a single SATA
disk, you have the option of striping (with RAID) or simply partitioning
the two disks with each project allocated a partition, which will keep
the seeks while working on that project localized.

One reason that the SATA disks are larger is that they are being
used as a less critical testbed to determine the failure rate until
someone decides whether they are reliable enough to be sold as SCSI
disks. All it takes is a swap of logic card to turn a SATA disk into a
SCSI disk -- or vice versa. The higher (new) cost of the SCSI disks
relates to the smaller customer base, and the extra testing which goes
into producing reliable disks for the high-end users.

So -- yes, the SATA disks will probably continue to be larger
than the largest SCSI disk -- simply because the platters and heads
don't have a long enough track record yet to be trusted as serious SCSI
drives.

Enjoy,
DoN.

--
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