Re: 306GB drives!

From: Jack Peacock (peacock_at_simconv.com)
Date: 08/19/03 

Date: Mon, 18 Aug 2003 17:12:53 -0700

"Bob Lail" <Robert.Lail@hp.com> wrote in message
news:btb0b.2619$3s2.1400@news.cpqcorp.net...
>
> Read the paper. It will enlighten you to the real differences between
> ATA and SCSI disk drives. They are VERY different and no one should be
> advocating replacing SCSI drives with ATA drives in Mission Critical
> applications unless they know and understand the risks they will be taking
> with their data.
>
Yes SCSI does have better reliability and queueing, but the real comparison
should be between ATA drives and high (and expensive) capacity tape systems.
When tape cartridges start to approach $100 each a quantity of big ATA
drives begins to look attractive as backup media to supplement archive tape.
For straight sequential transfers in a single task (i.e. the typical backup
while idle scenario: no advantage in cache size or elevator seeks, transfer
rate limited by disk speed instead of interface) ATA drives match Ultra2 and
come pretty close to U160 SCSI in effective transfer rate. I've been
running a few simple tests on W2K using the Symantec GHOST utility to backup
system images during upgrades and it's far faster than a tape copy to DDS4.
Difference is 500-600 MB/min on U320 to ATA vs. 60-100MB/Min on U320 to DDS4
(separate SCSI channels) with compression.

Unfortunately the only VMS system with an IDE interface I have at hand is an
old Alphastation 400/233, with an ATA transfer rate that is very competitive
with TK50s but not much else. It's a shame DEC/COMPAQ/HP never came out
with a good VMS supported IDE PCI controller board, one that supported
DMA-66 and above.
   Jack Pea***