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RaidArray

Summary

From inventgeek.com - How to build a cheap scsi raid array, with some very nice redundancy.

Motivation

Ever had a hard drive fail? I have had a TON fail. Yes I've had some that have never failed but when a drive does fail, it sucks big time especially cause usually you lose all of your data. Here, we build a Raid-5 hard drive array to prevent data loss and use old parts to save money.

Introduction

RAID stands for Redundant Array of Independent Disks. There are several levels of RAID, it is very easy to find more info about it on the internet, but the basic idea is to put your data across several drives, copying it so that if one drive fails you do not lose all your data. There are different methods of doing this, here we use RAID-5 which uses one drive for parity and the others for data. Actually all the drives are used for parity in the following way. If you have 4 drives, 3 will have data bits (1s or 0s) and the last drive will have a parity bit (1 if the number of 1s on the other 3 is odd, 0 if its even). Usually, you dont always use the same drive for parity in the sense that it rotates, the last drive might contain the parity at one level, then the next it will contain data and the third drive will contain the parity, and so on. This allows that if one drive fails, the values on it can be calculated from the remaining drives.

The idea with this project is to use somewhat older components to build a raid array which is useful and cost-effective.

What you'll need

-A Computer

-SCSI SCA Hard Drives

-SCSI Raid PCI card - I highly recommend the IBM ServeRaid series. I used the ServeRaid II (model 76H3587) which is about 10 bucks on ebay. I found drivers that works for Windows XP and linux here - just download the CD Image iso and burn it. I got really lucky and managed to get a card that was a spare for a server, had never been used but just sat in a closet for a while. It came with manuals, driver and configuration disks, everything. It really helped alot to have the manual but I'm sure you can either find it online or figure out the card without it. The trig for me was I had a disk I used to boot into the configuration manager for the card. I don't know if you can use this cd or not, I only used the cd for the drivers.

-A separate power supply (optional but highly recommended)

-Power splitters - unless you have a power supply with enough leads for each drive (and really long ones) you'll need these. I got mine from cableconnexion.com

-A case for the hard drives (optional)

-SCA 80 pin to 68 pin scsi adaptors - available on EBay, the title of the item I bought was "4PACK SCA ADAPTER 80F TO 68F ULTRA SCSI II/III LVD-SE" and I bought 3 for a total of 12 converters. Total was 53.82 including shipping, which divided by 12 comes out to about 4.50 each.

-68 Pin SCSI Cables - I was able to get a 4 device rounded cable - listed as "50 BLUE SCSI CABLE 4 DEVICE 68 PIN LVD 320" on ebay for 9.31 including shipping. You can buy really expensive cables at compusa or something but the three I bought on ebay have worked just fine. If you're scared of ebay you might find a link on the left of this page.

-Fans - these harddrives get REALLY hot. Fans are an aboslute must. I recommend 120mm fans because they move a lot of air but aren't too loud because they dont have to spin as fast. You can get these for less than 10 dollars each at newegg or on ebay.

Here are the parts I used and what they cost me:

Part Cost/Unit QTY Total Link
SCA 80 to 68 pin adapters 4.49 12 53.82 sca adapter on ebay
IBM ServeRaid PCI Card - 76H3587 7.00 1 7.00 ebay:76H3587
Seagate ST150176LC 50GB drives 19.88 12 238.50 ebay:ST150176LC
Scsi Cables - 50" blue rounded, 4 device 9.31 3 27.93 ebay:blue scsi 68 cable
Power Y Spliter .71 9 6.39 cableconnexion.com
Total 333.64

Steps

Getting the hardware set up is one of the quickest easiest parts of this project. Initializing the array takes forever though.

1. Turn your computer off

2. Plug the RAID card into a free PCI slot

3. Set up the cabling and jumpers. I had 12 drives on a 3 channel card, so 4 drives per channel. I mainly did this because I had 4 device scsi cables, you can put up to 15 drives per channel. You can really only use nine drives in one array though (I think - I split mine into two arrays). So, I used 3 power splitters to run a single lead from the power supply into four of the adapters. I set the jumpers 0 through 3 (or 1 through 4), plugged the scsi cable into each adapter, plugged each adapter into a drive, then the end of the scsi cable into the card. Once you do this for all your drives, you're pretty much done with the hardware portion.

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Sources and inspiration

Jared Bouck from inventgeek.com PoorMansRaidArray

Further Ideas

How to Keep Hard drives cool