[Gllug] SCSI Cards.

[Rich Walker]

In message <66E3124EE70FB04A96C81EF18C6C18B31D89BF at ex1.globus>
          "Paul Brazier" <pbrazier at cosmos-uk.co.uk> wrote:

> > Well, I'm a SCSI bigot; in particular, IDE doesn't support
> > disconnect-reconnect, which is a pain for non-hard disc devices.
> 
> Why is IDE cheaper and more popular then?
> I guess they're popular because they're cheaper :) but why are they
> cheaper?
> 
> Is it purely historical accident and economies of scale (think VHS/Beta)
> or are SCSI systems inherently more expensive to manufacture?

This came up on comp.arch a little while ago. It seems that, at some
point in history, drive manufacturers did use the same drive for IDE 
and SCSI, just changing the electronics. More recently though, they
have taken to differentiating the hardware itself. 

Typically, a SCSI drive of a given size will have more smaller
platters spun faster than the corresponding IDE drive. This produced
better seek times (less linear distance to move heads across),
better rotational latency (smaller => spins faster at same power
input, spins faster => less time to get to the sector), and greater
data throughput (more platters => more heads...)

Unfortunately, it ups the power requirements and the price. 

I think that FCAL drives are just SCSI with different electronics.
(If anyone has  two 18GB FCAL drives going spare or for sale, please
tell me...)

I think the rule of thumb goes:
   for lots of storage space, use IDE with RAID
   for low CPU usage, use RAID controllers or SCSI
   for hotplug/wierd devices/... use SCSI
   for reliability use mainframes.

hth


cheers,Rich.

-- 
Rich Walker: rw at shadow.org.uk (Shadow Robot Project)
http://www.shadow.org.uk        251 Liverpool Road
+44(0)171 700 2487                London  N1 1LX
"Sometimes after an electrical storm I see in 5 dimensions"
  -- Cornfed Pig,  Duckman.

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