Reply to mail from Leonard Zhang System Administrator ISD RVIB about Dumb question:
Which is "better" SCSI or IDE disks?
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> I think currently spinning SCSI hard disks on the world, either in servers
> or workstation, either in Unix/Linux or NT, is 50-pin old guys, no DPT disk
> cache or RAID. My comparison is base on this current real world. Not on
> the most up-to-date technology.
hmm. i *think* we have some old 50pin drives somewhere.
even in my home pc, i have a dual fireport 40 fuw card, non-differential
($149) and a fuw baraccuda 4.5g (@300) that was purchased last year.
the cost comparison is: ide, standard onboard, scsi card, $150. 4.5 ide
to scsi, scsi was about twice as much.
> At least Adaptec are still manufacturing and selling 16 bit SCSI card for
> about $A100.
a single channel fireport is about $70. fast ultrawide.
> No one denies SCSI's performance, expecially when you want hook up over 4
> devices. Those persons who asked the question do not have enough bucks in
> their pockets. My comparison is based on this ground. Everybody wants a
> Ferrari, but not everybody can afford. They buy Daiwoo not because they
> don't like Ferrari.
then state this specifically when qualifying your arguement. 16bit scsi
has been around for a long time, that's pretty fuzzy for an argument.
> DPT cache + RAID, not including SIMM, or error correction RAM is about $A2000
an ide controller performing the same function is similarly priced. (do
your shopping, you can get a much better deal on both)
> same either in SCSI or IDE. It depends on how many sectors/bits can pass under
> the aligned head. It depends on how fast the disk is spinning, and how many
> sectors the manufacture can squeeze in a cylindar.
which means the more versatile/advanced nature of the scsi software is
where the performance benefit is.
> If the disk assembly is the same, the MTBF is the same either in SCSI or IDE.
> The reliability is the same.
unless the scsi software intelligently acts on the drive, thereby
extending the life by smoother operations. this point however is rather
moot as one rarely sees a drive failure due to the head operations,
generally the drive fails due to a head crash or by drying of the spindle.
> High data transfer rate of SCSI can only be envisaged in the situation when
> several disk activity happens at the same time, especially there are quite a
> lot of devices on a same bus.
in both my server and workstation scenarios, i am doing multi faceted
accesses. streaming video, punching out web pages and file archives,
compiling, playing mp3s, streaming backups, etc.
> If you can manage to hook up all your devices in IDE, switching to SCSI may
> not get real benefit.
for single ended use such as a non multitasking system, this is very true.
for busy systems with scattered requests, particularly across multiple
devices, scsi is better.
-d
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