[lug] hard drive speeds

[Sean Reifschneider]

On Tue, Sep 28, 1999 at 02:54:41PM -0700, Jeffrey B. Siegal wrote:
>That's true in low-end systems, but the original message was asking about very
>fast (i.e. high end) drives.  Some of the fastest drives approach 40MB/sec in
>burst transfer rate (a few may even exceed that--I haven't looked recent), which

By "burst transfer" I presume you mean "In the drive cache, in which case it's
probably also in the system cache so the drive isn't being hit anyway"?
You rarely design a system for maximum burst capacity, unless that happens
more than infrequently...  My rule of thumb is 4 drives per interface --
PCs don't tend to have the capacity for taking a dozen PCI SCSI controllers...
The PCI bus is only marginally faster than 80MB/sec anyway...

I don't get the impression that Mike was talking about $30k server-class
machines with a PCI controller for each PCI slot...

Too bad RAM prices have doubled in the last month.  A month ago the price
difference between SCSI and IDE would buy you half a GB of CAS2 RAM...

>The numbers to look at are spin rate, seek time, and burst transfer rates.  How
>to interpret these numbers and make trade offs depends on the application.

I would argue that.  "burst transfer rate" tends to represent "out of the
cache" speeds, and has nothing to do with data density.

>In terms of price/performance, I would agree that IDE is respectable. However,
>the highest performance drives are still the Ultra2 SCSI drives, but you have to
>be willing to pay for it.

Oh?  What about the IDE RAID systems with a ton of controllers and one drive
per interface?  Many of them claim better-than-SCSI performance.

Sean
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