[rescue] u2 drive trays

Jonathan C. Patschke jp at celestrion.net
Mon Aug 18 16:10:36 CDT 2003

On Mon, 18 Aug 2003, Kevin wrote:

> Wow, UltraATA UDMA PIO200 whizbang EIDE sure is KEWL!!!

Kewl, yes.  Cool, no.

> Are you saying that with more than one drive per
> channel, you will take performance hits, even if both
> drives are of the same speed and only one drive is
> really being used?

Yes.  ATA does NOT negotiate well when you have more than one device on
the chain.  This is completely separate from the issue of negotiating
the entire bus down to the lowest present spec.  ATA has a design flaw
that causes 30%-60% of the effective throughput to be eaten up with
chatter/busywaiting when there are multiple periphreals present.  There
are benchmarks out there on the web, but I'm too lazy (read as: busy)[0]
to look them up right now.

[0] Or do I have that backwards?  I can't tell.
Jonathan Patschke   )  "We're Texans.  We figure out ways to do these
Elgin, TX          (    things..."                    --Bill Bradford

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