IDE vs. SCSI hard drives

[Jonathan Meyer]

talvola at danube.Berkeley.EDU (Erik Talvola) writes:

>  I will shortly be purchasing a new hard drive, probably the Conner 200 meg
> hard drive, which people have given me good reviews about.  It is available
> in either IDE or SCSI, and I was wondering about the advantages of each.
> I know the IDE is supposed to be faster under DOS, but then again, the SCSI
> can have a tape drive hooked up later possibly, and may have better Unix
> performance.  I am not even sure if IDE drives are generally supported under
> Unix.

This should probably be on the list of frequently asked questions.
I'm not an expert, but here's my answer:

The IDE drives are good, and as far as an AT-386 class machine is
concerned, they are identical in interfacing terms to an ST-506 (ie.
normal) hard disk controller/drive. The nice thing about IDE is that
they are simple to install, simple to setup, and they are
appreciably faster than the ST-506 in some cases, especially the IDE
Conner 200MB drive, which is a peach of a drive. An IDE drive will
work under any unix so long as the drives parameters (heads, sectors
etc) appear in that unixes tables, or the unix lets you enter your
own drive specifications. In DOS, no special drivers are required,
so they are much less hassle than a SCSI disk.

Asking for the difference in performance between IDE and SCSI is a
little unfair: The drawback of IDE is that you are stuck with what
controller hardware the drive manufacturer puts on their hard disk,
since the bus card basically contains only a small amount of
buffering circiutry. SCSI, on the other hand, varies enourmously
according to what controller you are using. With a basic SCSI
controller, the difference in performance between IDE and SCSI is
probably negligable. However, you can purchase some very
sophisticated intelligent SCSI cards (Adaptec, SCSI-2000, ...) which
will increase your performance dramatically, and take SCSI into a
different league from IDE. These SCSI cards often provide UNIX/DOS
drivers for things like tape drives, CD roms, worm drives and more.
As a consequence, they are much harder to set up, install, etc. but
give you greater flexibility. Of course, these controllers cost a
bit as well.

Which to get? I think you'd be happy with an IDE, unless you have
some demanding computing to do, or are about to add lots of
drives/tapes to your machine. You can always get SCSI later, and use
it as well as IDE in your machine.

You could get a basic SCSI card and drive, and upgrade your card at
a later date. But be prepared for hassle with SCSI - make sure your
card is supported by the relevant unix system.

Jon.

PS. For the record, I have a 100MB Conner IDE drive and a 100MB
Seagate SCSI drive with a WD-7000-FAST controller. No, I'm not
telling you which I prefer!










In any case the AT BUS has a lowish bandwidth, so