[K12OSN] Hard Drive Upgrade Quandary

[Ken Meyer]

Excuse me, but I have not asserted results of my personal experience in any
respect.  On the other hand, I have been a primary organizer for the Greater
Seattle Linux Users Group for several years, I have engineering degrees from
Princeton and the University of Washington, and many years experience
insuring the integrity of flight-critical digital systems.  What's your
claim to authority?

I quoted a website that conducts very thorough testing of hard drives, and
which has been around for a long time.  There is a lot of insightful
tutorial material on the site, and I see no reason to question the generic
quality of their conclusions.  And I referenced Chris's comments to this
list about thoughtful experiments and contacts with 3Ware that he has
conducted.

In other words, ALL of the information that I have cited IS from people who
have serious experience with QUANTITATIVE evaluations of RAID
implementation, and who are not limited to assessing whether the system
locks up or crashes or not.  "Works fine for me" is useful information, but
does not necessarily indicate that optimum performance has been achieved.  I
didn't even mention the quality of Linux software RAID, which has engendered
some really very disparate opinions in the past.

In any event, I urged everyone to consult these references and evaluate
them, and I even allowed that others felt that striping was more beneficial
than storagereview maintains, though they have not provided any numbers that
I know of.

Is it the address to "Mr. Linux Bigot" that is the real, underlying source
of your ruffled feathers?  That was said in jest, as this entire, wonderful,
eminently helpful group at least leans in that direction, with the very most
charitable opinions expressed about M$ falling into the category of
"tolerance" or "accommodation of the inevitable."  At the least, as I said,
the appellation is certainly not a unique identifier within this group.

Ken Meyer

PS  You might consider not posting in HTML, if you profess to be so in tune
with the proclivities of this group.


-----Original Message-----

From: k12osn-bounces at redhat.com [mailto:k12osn-bounces at redhat.com]
On Behalf Of Brian Chase
Sent: Friday, November 26, 2004 2:50 PM
To: kmeyer at blarg.net; Support list for opensource software in schools.

Subject: Re: [K12OSN] Hard Drive Upgrade Quandary

Mr. Meyers experience with Linux and setting up RAID is lacking in his
email.  Do we want to listen to him?

Anyone can read articles that might be slanted to begin with.  Only the
folks that have hands-on experience can offer advice from a more practical
perspective.

Who would you believe, someone who has done it, or someone who reads alot of
tech articles?  Your choice.....


Ken Meyer wrote:

Mr. Linux Bigot (that's not a unique identifier around here) --

I recommend that you search the archives of this group for further
information about this subject, which is one of those periodically appearing
ones.  A couple of previous items:

www.storagereview.com maintains that there is very little performance
benefit in striping drives (RAID 0), but of course, you multiply the
jeopardy of a failure that will take you down by the number of drives
striped-across.  Others have said that the performance enhancement is
greater -- but, Bottom Line, caveat emptor.

Of course, the mirroring helps the reliability aspect, but if you are into
four drives, why not go for RAID 5, which as I understand it, will only cost
you one drive's worth of overhead?

Chris Kacoroski has done experiments (results in the archives) and has found
that the 3Ware RAID boards do well for large file transfers, but have real
performance problems handling small, random file transfers as the thin
client solution will create.  Apparently, he even involved the 3Ware folks
in trouble-shooting.  Perhaps they have been able to address the problem
since then, but as I recall, Chris has another recommendation for RAID
controllers for use in LTSP systems.  Again, caveat emptor.

Ken Meyer


-----Original Message-----

From: k12osn-bounces at redhat.com [mailto:k12osn-bounces at redhat.com]On
Behalf Of Calvin Dodge
Sent: Friday, November 26, 2004 9:31 AM
To: Support list for opensource software in schools.

Subject: Re: [K12OSN] Hard Drive Upgrade Quandry

Liam Marshall wrote:

I would like to get a Promise IDE raid controller, either the 4 or 6


Make sure it's compatible with a stock Linux kernel.  Typically, the
low-priced
RAID controllers are software-based (the driver hides this fact from the
operating system), and sometimes the drivers are provided in binary-only
format
(like the Promise controller at one customer's location, which provided
modules
only for kernels from RH 7.2).  You're really best off with a card with
open-source drivers (like 3Ware, though I suspect that's out of your price
range).


channel version, haven't decided yet.  I was going to put on it 4 - 80
GB EIDE hard drives with 7200 rpm and 8MB cache each.  I would use these
in a raid 0+1 or raid 1+0 configuration.  It is my understanding that
this will give me the best of both mirroring for redundancy, and
parity/spanning for performance.


Yes, although 2 80 gig drives cost quite a bit more than 1 160 gig drive.


If I am right in my understanding of raid levels 4 - 80GB drives in such
a configuration will give me 160GB of storage space, with the other
160GB of the drives being used in a mirrored capacity right?


Yes.

Calvin
--
Calvin Dodge
Certified Linux Bigot (tm)
http://www.caldodge.fpcc.net


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