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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.'"
Depending on the your budget here in the UK you can get an 80Gb HDD for around £35, so split over some time you should be able to afford two (or an extra one if you already have one). This is a good enough reason for anyone to try RAID.
I myself currently have it setup to mirror my data across two 80Gb drives... Four months ago one of the hard disks died (funny buzzing sound, no access) but the manufacturers three year warranty was still valid, so I returned the drive to them for a free replacement. I received the replacement drive and shoved it in, mirrored the data back onto this new second drive and continued as before. If I hadn't have had this setup that data could have been permanently list. It also saves me from writing ten DVDs to store that much.
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.
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.
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No, it's not "Real-Time" but it suits our needs in our home office situation.
I use "Smart Synch" software to incrementally copy the desired directories from the working computers to a "Backup server", an older Celeron machine on the network. Separate partitions are set up for each computer that is being backed up. At Midnight the incremental backups are made.
Then at 2:00 a.m., Smart Synch running on the backup server makes another backup to a USB hard drive plugged into it. That USB HD is on a regular plug-in timer so that it only runs during the time of night when a backup to it is being done. The idea there is that the running time is limited and drive life is extended. Weekly, a backup DVD is burned and stored off site. Am I being anal? Maybe.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
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.
If that RAID array is the only place you are storing all those home movies, I highly recommend you take a backup to some other kind of media. As other people have said, the RAID controller is a single point of failure. If you lose that, you lose the lot. And there's no guarantee that another controller will be able to rebuild it. Sad but true.
Serving Suggestion: Defrost