[K12OSN] Hard Drive Upgrade Quandary

[Ken Meyer]

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