[KLUG Members] Re: RAID

[Bryan J. Smith]

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On Sun, 2002-12-15 at 17:25, Adam Williams wrote:
> "Should" is an important clause,  I've been bitten hard by lots of
> "should"s in the past and am very skeptical.  Minor version numbers have
> often rendered hardware components incompatible and reading the never
> ending torrent of poorly written docs is just too much effort.  Out of
> principle I avoid "integrated" components except for the most basic
> (standard IDE, VGA for a console, etc...) uses.

Well, if you want to know how I _really_ feel, I think those "BIOS-only"
ATA RAID cards are complete wastes of money.

> Sure.  But my only experience is with SCSI.

Both the Promise SuperTrak and Adaptec 2400A are whoafully underpowered
compared to most SCSI RAID cards.  They throw in the cheapest,
lowest-end i960 chips.

> ATA technology just doesn't interest me.  I find the price difference
> for reasonable amounts of storage to be negligible,

"Reasonable" is relative.  "Reasonable" to me is 150-200GB on my home
workstation, and 200-300GB on my home server.  Of course, I'm an
engineer and I produce an enormous amount of temporary files.

> and one avoids all the bizarre versions, hacks, workarounds, and
> lame products that come with ATA.

Don't confuse "BIOS-only" ATA RAID with "True hardware" ATA RAID.
"true" ATA RAID and "true" SCSI RAID are the _same_design_ -- _exactly_!

As you said, "But my only experience is with SCSI."  I'm going to have
to insist you are talking from a point of ignorance in that case.

I've used most brand of SCSI RAID cards with Linux, NT and even OpenVMS
on both x86 (except VMS) and Alpha.

> I know what my SCSI card is,  I know it works with 99.999999999% of
> SCSI drives,

Depends on your viewpoint.  E.g., 3Ware cards use FPGAs for their ATA
controllers, so they can be upgraded to newer ATA standards and speeds.

> no magic cables required, etc....

Okay, now you're just being argumentative.  If anything, SCSI is the
_king_ of cable confusion dude.

Of course, SerialSCSI _is_ being planned as well.

> Sure you can't get a 10000TB SCSI drive at Best Buy for $19.95 + tax,=20
> but 9 & 18 Gb drives are available cheap in abundance, and 36Gb aren't
> that bad.

Cost, cooling, power, etc...  Gets very hard to accommodate.

Secondly, even 10000rpm SCSI disks of previous-gen technologies can be
outperformed with latest-gen 5400rpm ATA disks at many operations.

> An IPS controller can be found for ~$50-$100, less than what some
> ATA-RAID cards sell for.

The controller, yes.  But when you need 100GB+, the cost/MB clearly is
the disk, not the controller.

> And one can stack a bunch of drives up in an external cabinet with
> dual P/S and four fans (~$150 on E-Bay).

First off, trying to buy used hardware doesn't go over well with
management.

Secondly, 4 x 80GB in RAID-10 is cheap, easy and fits in most,
well-designed PC chassis while still being adequately cooled.

> Drive failures?  I'm still using a cabinet full of 9Gb FH Seagate
> drives, and they may still be spinning when I'm worm food.

True.  Many ATA devices are not designed for 24 x 7 operation.  People
forget that.

> They don't set any speed records (but you might be surprised) but the
> majority of the crap on a home system is totally insensitive to drive
> performance,  just put what matters on fast/new drives (yawningly easy
> with LVM support) and continue to use all the drives you've already
> paid for until the croak (still waiting).

Well, I like to match up models for efficiency.

> People love to toss around MTBF numbers, etc... but it is my significant
> cumulative experience that ATA drives are disposable - in large part
> maybe just because they have to be located in the same case as all the
> other hot junk - unless one buys extra fans and drive bay coolers
> and.... so the price differential is even further diminished.

Yes.  Cooling is important.  Of course, if you purchase a half-way
descent case with active cooling over the drives, this isn't an issue.

My workstation (4 x 7200rpm ATA) and server (4 x 5400rpm + 4 x 7200rpm
ATA) drives stay cool to the touch thanx to an 80mm blowing over them in
my Antec cases (SX600, 1000 and 1200 cases are used in my home).

> I'm not interested in starting a SCSI/ATA holy way,

I think you just did (again).

The _difference_ between you and I is that I've used _both_, whereas you
have not.

> people should use whatever works for them.

> Just saw my message being interpreted (which
> is just fine) and thought I'd weigh in with my insight, knowledge,
> ignorance, experience, prejudice, and general laziness.

Again, I do have your same attitude in regard to SCSI RAID.  I've
supported production networks in my career too.

But I've also made sure I've used _real_ ATA RAID solutions.  And there
is a heck of a lot of difference between those "BIOS-only" ATA solutions
and the ASIC+SRAM design in 3Ware products.  Especially for RAID-0, 1
and 0+1 (aka 10).

Heck, IMHO, if you're going to go with a microcontroller+DRAM RAID
solution, it should be SCSI instead of ATA.  Why?  The blocking I/O
design kills all the performance advantages of ATA anyway, so you'd be
better off served by SCSI.


--=20
Bryan J. Smith, E.I. (BSECE)       Contact Info:  http://thebs.org
[ http://thebs.org/files/resume/BryanJonSmith_certifications.pdf ]
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