From: Randal Whittle (rwhittle_at_usa.net)
Date: Sun Apr 23 2000 - 00:35:24 EDT
At 08:43 PM 04/22/2000 -0400, you wrote:
>Heh... We have better disks--they're called Ultra SCSI 160 which can transfer
>160M/s, which is about 2.4 times faster than the "new improved" 66M IDE disks.
Its also a phantom number that only matters in burst mode between
SCSI devices on the same data bus--and its *very* rare. Hey, I like SCSI
as much as the next guy, largely because of the lower CPU overhead
necessary to run it, but the fact of the matter is that the most important
performance figure of any drive, perhaps aside from the access time, is the
sustained transfer rate.
When it comes to the sustained transfer rate, only the very best
10K RPM SCSI drives (like the Seagate Cheetah) are any better than the best
EIDE drives, and then not because the HD itself is so inherently superior,
but because they put SCSI as the interface for that high-performance HD
(instead of EIDE) because its final destination is most likely a network
server, where multiple-HD's are the norm, and where SCSI prevails.
At any rate, if you look at the sustained transfer rate of the
very best EIDE drives (say, Maxtor's DiamondPlus series) and compared that
to the best SCSI HD's, you'd see they are almost the same. The extra
bandwidth available on the SCSI bus is only useful when multiple devices on
the same bus are moving data around. The peak drive transfer rate is the
peak for that drive, and any extra bandwidth isn't necessarily going to do
a darn bit of good. Hence, for the most part (except for some
side-benefits of SCSI, like lower CPU overhead), having a single HD on a
SCSI bus isn't necessarily "faster" than a single EIDE HD.
>Why SCSI disks don't exist in the form factor for notebooks is something I
>have
>never understood. There is nothing in the SCSI hardware that couldn't be
>put into
>the size of the small disks that ThinkPad's use, so I guess it boils down to
>economics. Spending an extra $50 (although I can't imagine it would be
>that much)
>for a faster disk/controller on a laptop just seems to be beyond
>people. Price rules
>in the laptop world, just like it does in the desktop arena.
I agree--SCSI would be nice. On the other hand, unless there's a
need for it, its just extra cost. For the most part, in a notebook, its
just extra cost. NB drives are inherently slower anyway, and as such, not
really capable of taking advantage of any extra bandwidth SCSI offers over
EIDE anyway.
I use SCSI on my desktop, but except for my high-bandwidth-sucking
video-capture needs, it wouldn't even be necessary. A good EIDE drive
could still do the job, but the interface sucks up more CPU overhead and in
general, servo-embedded HD's (to prevent the need for recalibration--in the
middle of video playback or capture), are pretty much only SCSI. They
don't *have* to be, but they just are. Nevertheless, a lot of people in
the video-editing area have had excellent results using a plain 'ol EIDE
drive, though the caveat is that they need to have a separate drive from
the one that runs the OS, to avoid having the drive seek for various OS
pieces it needs.
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