On Jun 16, 2010, at 8:15 AM, Dan wrote:
> At 9:37 PM -0700 6/15/2010, Jeffrey Engle wrote:
>> ok, new to the scsi thing as you might have guessed. it just seems to me
>> that it's such a "yesterday" technology, why is it still in big demand?
>
> IEEE-1394, aka Firewire, is a subtype of SCSI-3.
>
> SCSI-3 SPI, from 2003, btw, does 5120 Mbps (5.1 Gbps).
>
> Why nothing newer? Because HD tech hasn't caught up to those speeds yet!
> Sure, some drives are beginning to fake it with big buffers (caches), but
> that only improves performance in certain limited situations.
Actually, in the enterprise world, SCSI has given way to SAS ('Serial Attached
Storage') drives, but improvements in SATA have meant that, except for the most
demanding throughput needs, SATA has the bulk of the market.
Server grade SATA drives are available, and have, at least in our experience,
been pretty reliable. We've lost zero drives in our SAN since we started using
it three years ago, which is a BETTER service record than our old SCSI RAID box.
We still use a SCSI SAN on our Mail server system, but when that gets replaced
we're likely to replace it with a SATA SAN; we just can't justify the cost of a
SAS SAN. Our file servers (now at 6Tb and growing) all use a SATA SAN, and it's
proven very reliable and more than sufficient to keep up with I/O demands.
(and if you're dealing with large amounts of networked file server space, SAN
is head and shoulders ...and torso and hips and knees and ankles...above any
other solution out there. Need more space? add more drives to the SAN box or
buy another box and stuff it fulla drives. expand your volumes on the fly and
suddenly your serves think that their shared volumes are now twice as big...all
live, unless your %...@#!$@# backup software has a hidden 2TB limit for the
volume format that makes you have to nuke the new volume, reformat and restore
from tape....for two days...)
Frankly, I don't see any reason to invest in a SCSI solution on a standalone
system, or even most servers. If a bunch of SCSI drives and the expensive
controller fall into your lap, you'll see improvements in disk IO and if disk
IO is your bottleneck, you'll see an improvement in performance.
If your bottleneck ISN'T disk IO, then you've just invested in a very very
noisy space heater. 15K SCSI drives are hot and loud.
As for connecting a bunch of drives, if you have need of that much storage,
it's cheaper to get a FW800 RAID box and stuff it full of SATA drives letting
the box sort 'em out, or go bigtime, get a Fiber Channel card and connect it to
a SAN, but you're talking $5K minimum for that kinda setup.
If you're editing Ken Burns' latest opus, though, that's a worthwhile
investment.
Just remember with great disk capacity comes great backup needs. We just spent
$18K to upgrade our tape backup systems to (barely) keep up with our ever
increasing file server space; we really need to spend $30K on a disk-disk
system.
--
Bruce Johnson
University of Arizona
College of Pharmacy
Information Technology Group
Institutions do not have opinions, merely customs
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