[ILUG] Why RAID

[John Coleman]

On Wed, 14 Jul 2004 18:05:41 +0100, Gareth Eason <bigbro at skynet.ie> wrote:
>     Dealing with digital audio and video, RAID provides a hardware
> method of abstracting the bandwidth required across multiple disks.
> You've all heard of SCSI320. How many of you thought you could actually
> get 320MB/s from a single disk? However, put a (RAID) array of them
> together and you start to make better use of the bandwidth available on
> the bus :-)

about 3-4 15Krpm drives will fill a single UW320 channel.
For really big arrays you'd be looking at 4-channel cards for optimum
throughput.
This is obviously subject to several other factors :)

> 
>     The original question, posed by Timothy was, "Reading about all the
> problems with RAID, I wonder why people bother with it? Is it worth the 
> hassle?" In response, Yes! Yes! And wholeheartedly, yes! But you have to
> use RAID for what it was made to be used for.
> 
>     Best regards,
>     -->Gar
> 
> 
> 
> 
I'm looking at building a RAID5 array for non-production environment.
It'll be an ongoing expansion due to lack of immediate funds.

Base system has already been built by me:
2x AthlonXP2400+s with L5 bridge-mod to MP2400+
1Gig stick Corsair ECC PC2700 DDR - looking at getting another 2x 1Gig ECC
MSI K7D-MasterL (AMD 760MPX-based - 2x 64-bit/66Mhz 3.3V slots)
Chieftec Matrix full tower
Chieftec 360W psu

Planned near-future upgrades are
a) a 460W+ Fortron/Enermax PSU (solid rails and quality)
b) LSI Megaraid Sata 150-6 (hardware Intel XOR engine, 6-Sata150
channels, native kernel support, shows up as /dev/sda device) +
battery backup card
c) 3x Hitachi 7200rpm 250Gig 8Meg Sata drives
d) a butload of 80, 92 and 120mm Papst fans and a few bits and pieces
for a PWD/Rheobus temp controller.
The fans are quiet enough at stock rpm, but I'm going to tie the speed
to the surface temp of the drives, with the fans mounted in front of
them blowing cool air over the cages.

I will eventually fill the card with 6 of the drives, but at the
moment I'm unsure if I should go for 5x raid5 disks + 1x hot-spare or
what.

This is hardly production environment, but I abhor optical media as a
primary source and disk-swapping and a nice big redundant array to
hold all my legally own CDimages, music and downloads (game patches,
mods, photos, archives) is a nice idea in my mind.
I say "redundant" because I will have 2 levels of resilience - a
surge/spike protector/UPS and the RAID/hotspare - enough to let me
shut down the box before stuff is lost.
The controller is fairly common and LSI have a good reputation, so I'm
not too worried from that pov.
The best thing is that if anything is lost, it's not *that* big a deal
as I will have DVD-R (on doog media) backups of the "really" important
stuff.
May also have a RAID1 array chucked into the box aswell, plus my own
desktop system.
Again, this is not a production environment.

>From recent experience in a semi-production environment, if you
haven't sorted the Layer0 side of things you're going to have drives
dropping like flies.a poorly cooled hard drive won't last 6 months of
24/7 work.

JohnC