Quoting Ian C. Sison ([EMAIL PROTECTED]):
> First of all, please understand my replies in the context of my original
> posting:
Naturally.
But I was responding to _one specific comment_ you made about UDMA 133.
> The advantage of disconnected operation only comes in when you have more
> than one scsi device in the chain. IDE RAID solves this problem by having
> multiple IDE channels, with only one device connected to each channel.
That is true, but irrelevant to your earlier statement, and to my
critique of it. A point we will return to.
> Also, By faster access i meant to compare to previous IDE technology,
> which did not support RAID, and was contrained to dismal data transfer
> rates on the wire.
But that is precisely where your assertion was misleading: In previous
IDE technology (such as the ATA/66 and ATA/100 bus-transfer specs),
there was absolutely no way to ever saturate the bus, because only one
drive on the chain could be active at a time, and no single hard drive
of current or recent production can read data quickly enough to saturate
those buses even under ideal conditions, let alone with any significant
frequency. And of course the same is true of ATA/133 ("UDMA 133"), for
the exact same reason.
Thus, claims that ATA/133 (or predecessors) yields "faster access" are
rubbish. Inherently.
> With UDMA66-133, the issue of data transfer no longer
> was in the speed of the 'wire' but in the actual data transfer from disk
> platters to the underlying disk electronics, which is currently the
> bottleneck in both scsi and ide systems, in single drive installations.
The latter statement is manifestly incorrect. By far, the bottleneck in
hard drive setups generally is physical disk access.
> I get your point that SCSI allows you to aggregate the bandwidth
> consumption on a single bus. I hope you get mine when i said the latest
> ATA is "faster" then its previous incarnations, when the wire speed was
> the limiting factor.
No, that is rubbish. There isn't a hard drive that can put out even
ideal-case disk reads that quickly. (I'm not counting reads from
cache.)
> Again, I'm merely pointing out (as in my original post) that IDE RAID
> solutions approach the speed and reliability of SCSI based systems for a
> fraction of the cost.
Here, you are changing the subject. I was addressing the merits of your
(quite wrong) assertion that UDMA 133 yields "faster access".
And I am declining to change the subject as long as efforts to obscure
my point continue.
--
Cheers, "Learning Java has been a slow and tortuous process for me. Every
Rick Moen few minutes, I start screaming 'No, you fools!' and have to go
[EMAIL PROTECTED] read something from _Structure and Interpretation of
Computer Programs_ to de-stress." -- The Cube, www.forum3000.org
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