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Basics of RAID
Doggie Fizzle writes "RAID has been common in business environments for ages, and is now becoming more viable and popular for personal computers. This article focuses on the the basics of RAID, and spells things out for beginners or tech veterans. From the article: 'The benefits of RAID over a single drive system far outweigh the extra consideration required during installation. Losing data once due to hard drive failure may be all that is required to convince anyone that RAID is right for them, but why wait until that happens.'"
That's an awful lot of ads for a re-hash of well-known info. Are the editors sure this is frontpage worthy? It looks like a blatant attempt to get page views to me.
http://raid.com/
http://www.killsbugsdead.com/
There's an excellent guide to RAID levels (with pretty diagrams and such) at http://www.acnc.com/raid.html
A source of information with far better content, that isn't simply an excuse to sell ads.
Wikipedia
Here is a link that explains the basics of computer hardware; I think that it's a good companion piece to the RAID article: http://www.angelfire.com/rings/judy_patch/
Okay I guess it appeals to geeks and fancy computer modders and all. But really, when it comes down to it, a decent main hard-disk, a tray in the second bay for backup hard-disks, and a reasonable backup regimen that people keep up is all a "personal" computer user needs.
Personally, I have 3 backup hard-disks, one that keeps a "clean" base system that I update every 6 months or so, and 2 that I do full differential backups on every 3 days. The "clean" hard-disk is kept off-site, and a script tells me when to do the backups on the other 2. And for very very important files, I just write them on a CD on the spot.
With that, I've yet to lose a single file since I started using Linux in 93 or 94. My solution is cheap and doesn't involve fancy raiding. And I'm quite sure I overdo it, most people could do just fine with one main hard-disk, one backup hard-disk and a little discipline.
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
With RAID, you still have a single point of failure. Instead of it being your hard drive, it is now your RAID controller. So what is the advantage?
Since a RAID controller doesn't have moving parts, is it less likely than a hard drive to fail?
Don't forget that Friday is Hawaiian shirt day.
IDE HDD Talking to IDE Controller:
HDD: I'm gonna need more time for that write
Contr: Yeah OK, go ahead good buddy
Contr: What's up?
Contr: What's up?
Contr: Error: Drive controller timeout error
SCSI HDD Talking to SCSI Controller:
HDD: I'm gonna need more time for that write because I found a bad block
Contr: Yeah OK, go ahead and remap that bad boy
Contr: What's Up?
HDD: Need more time to map that bad block
Contr: Yeah OK, go ahead
HDD: All done, grabbing the next command in the queue
Alternatively to DVD backups, you can also sync up your data on a regular basis to an external hard drive. This doesn't protect you if your house burns down, like DVD backups kept in a safety deposit box would do, but it does help you restore lost data after it gets corrupted.
Ultimately, all these solutions require varying amounts of money, time, and effort, so you just have to decide what level of security you require and what you are willing to pay for it.
For those who have run out of internal space in their boxes, and who don't have external SATA or expensive hardware boxes, you can run RAID over Firewire.
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The problem, however, is that out of the box Windows refuses to "promote" an external disk to dynamic, which is required on all post-NT4 rigs for RAID.
The solution is to add a semi-documented Registry flag, EnableDynamicConversionFor1394
HOW TO: Convert an IEEE 1394 Disk Drive to a Dynamic Disk Drive in Windows XP
Couple that with a cheap 4-bay firewire JBOD box and any spare old enclosures and you are set!
I run 2TB in various RAID configs on my Windows server (main and near-line storage). Have done so since 2002. No problems with the external boxes. The support for external firewire RAID is a little gnarly in Windows 2000 - volume must be mounted as a named virtual directory and cannot be mounted as a letter drive. Later Windows give you both options.
Da Blog
Ultimately, what it comes down to is that mirroring merely makes the hardware more reliable, it is not a backup technique.
The higher the technology, the sharper that two-edged sword.
I worked for years in development of RAID solutions for a major manufacturer. One of the problems with selling RAID solutions is the lack of understanding, or the prejudice and bias of the people who were supposed to be specifying and buying the hardware.
The 'tutorial' of the parent article is talking in kindergarden terms, oversimplifications and obsolete term, and overlooking some of the issues with using RAID. It's a good example of the true lack of understanding about the subject. By now, there are so many types of solutions that the term RAID hardly applies. But, even 10 years ago companies like Compaq had innovative rudundant storage solutions that were enterprise ready.
Best regards.
Ultimately, what it comes down to is that mirroring merely makes the hardware more reliable, it is not a backup technique.
It can be part of this nutritious breakfast^W^W backup technique:
0) shut down the box
1) swap a fresh/new/wiped drive for one of the mirrored drives
2) rebuild the RAID
3) store the just-pulled drive appropriately (e.g. off-site) along with a second identical RAID controller
Now if the machine goes completely belly-up (as in a fire) the user can install the secondary RAID controller and the data-laden drive in a fresh machine, add another fresh/new/wiped drive, and rebuild the RAID in the new machine. This may not be terribly convenient nor perfect for everyone but it will be effective.
Remember, kids: just because a particular technique doesn't perform a task all by itself (in this case RAID 1 != backup) that doesn't mean it can't be part of a larger picture.
I want to drag this out as long as possible. Bring me my protractor.