Hard drives fail, and they do it much more often than we'd like to think. Even if you've set up automated hard drive backups, you're not necessarily getting the best backup bang for your buck—especially if your operating system's main hard drive fails. Even if you've been backing up your important files, you'll still need to reinstall your OS and go through the pain of copying your files back to your new hard drive, installing new applications, and setting up your system to how you had it. There's a better way, my friends. With a RAID 1 array, you'll always have a perfect backup of your hard drive so that—in the event that one drive fails—the other will seamlessly pick up where it left off. That means no reinstalling your operating system, no reinstalling applications, and no time lost in the event of a hard drive failure.
If you've never heard of RAID (or Redundant Arrays of Inexpensive Disks) before, it's a relatively old technology that supports the use of two or more hard drives to do things like improve hard drive performance or set up data redundancy. The RAID level we're going to look at today is called RAID 1, and its job is to mirror all of the data between two hard drives. RAID mirroring provides you with real-time, on-the-fly,
bulletproof hardware backups of your entire hard drive, operating system and all. The best part: It's easy to set up, and once you do, you can completely forget about it.
That sounds expensive/hard to set up/like it'll slow down my computer! Fear not, RAID is supported by most modern motherboards, requires only one extra hard drive that is the same size as or larger than the drive you want to mirror (identical drives are ideal for RAID but not required), and it won't slow down your computer in any practical way. In fact, the RAID mirroring we're covering today happens at a hardware level, meaning you aren't even running any special applications on your operating system to use RAID. It all happens in the background, so once you set it up you can completely forget about it. If one of your drives happens to fail, your RAID controller will alert you and you can continue booting from the one good drive and replace the bum drive to repair your RAID mirroring whenever you get a chance.
Still think it sounds a little over your head? It's not—setting up RAID 1 mirroring is a breeze, and I'll cover it below in detail.
NOTE: Not all motherboards support RAID configurations, nor are all motherboards consistent in how to set up RAID. Consult your motherboard's manual for specifics on your motherboard. RAID mirroring is not a replacement for backups of important files.
Install Your Hard Drive(s)
You can either set up a RAID configuration with two fresh hard drives or with your existing hard drive and an empty drive that is as large as or larger than your existing drive. At the very least, you'll probably need to install one new hard drive, which we've already covered in detail. If you've never installed a hard drive, give it a look—it's really much easier than you probably think.
Not every plug on your motherboard supports RAID, so you'll need to consult your motherboard manual to make sure you've got your hard drives installed to the right controllers on your motherboard. Normally there will be at least one pair of plugs right next to each other on your motherboard that will be the matched pair you'll need to install both of your hard drives to (see picture for the two plugs on my motherboard, an ASUS A8V).
Enable RAID in the BIOS
Now that your new hard drive(s) is installed, it's time to enable RAID in your BIOS. Reboot your computer, and at the BIOS boot screen (the screen that loads before your operating system loads) hit Delete (or whatever key your BIOS prompts you with) to enter the BIOS setup.
Again, you may need to consult your motherboard's manual to make sure you're tweaking the correct BIOS setting, but for the sake of demonstration I'll show you where mine were. In the ASUS A8V board I'm using, go to the Advanced tab, then Onboard Device Configuration. I installed the hard drives to the Promise RAID controllers, so I've set Onboard Promise Controller to Enabled and then the Operating Mode to RAID (see screenshot above).
Set Up Your RAID Array
After you've installed your hard drives and you've set your BIOS to use RAID, you still need to define your RAID array. The first time you reboot, the RAID configuration utility will alert you that you haven't defined your array and prompt you to run the setup utility. On my computer I had to press Ctrl-F to enter the RAID utility, but again, your board may vary.
Once you enter the RAID configuration utility (mine's called FastBuild), setting up RAID is usually pretty simple. To configure a mirrored RAID 1 setup on my system, I first went to the Auto Setup option, then followed the simple on-screen instructions to create a new array with my hard drives in a mirrored mode. In the Auto Setup options, that meant telling the utility to optimize the array for security.
When I saved my choice, the utility asked me if I wanted to duplicate an existing disk image to an empty drive or create and/or quick initialise the drives. Since both of my drives were new, I chose Create and Quick Initialise; if you were setting up RAID 1 mirroring with an existing drive, you'd want to choose Create and Duplicate. If you choose the Create and Duplicate option, the utility will proceed to duplicate the existing disk image onto your empty drive. Hard drive duplication can take over an hour, so make sure you've got a bit of time on your hands if you're duplicating.
When you're finished initialising your new array, quit the utility and restart your computer. This time, instead of being told that no array is defined, you should see a message describing the array you just created and indicating its status (Functional!). Everything you do from here on out will be mirrored exactly on the two drives. If you're starting with empty drives, now's the time to install your operating system. Just install like you normally would—the RAID configuration we set up is already mirroring everything that's happening.
At this point you're living the good life of RAID 1 mirroring, comfortable in the knowledge that you have a live-updating, fully backed up version of your hard drive at all times. Every application you install, every document you create, every tweak you make to your operating system is exactly mirrored on both drives. So what happens when one of your drives in the array decides to go boom?
What Happens If a Drive Fails?
The first time you start up your computer with a bum drive in your array, you'll see alert message like the one in the picture above. Notice that my array status has changed from Functional to Critical, and I'm told that a disk member of my mirrored array has failed or is not responding. The array is still functional, inasmuch as my operating system will still boot and run as though nothing at all has changed, but I'll no longer be mirroring my data between drives. That's not a huge deal by any measure—it just means that you're running like you did before you set up RAID, with one unmirrored drive.
You'll be fine running on just one leg for a while, but just think—if that bum drive had been your lone drive, you'd be out of luck. With those horrible thoughts running through your mind, you'll definitely want to repair your array to ensure that if your other drive up and died, you'll be just as prepared. Here's how that works.
Repair Your Array
First you'll need to figure out which drive failed. The easiest way to do this is probably to unplug one drive at a time and try rebooting your computer. If your computer continues to boot into your operating system, your good drive is still plugged in. If not, you've found your dead drive.
Now it's simply a matter of replacing the bad drive with another new one, remembering that your drive must be as big as or bigger than your existing drive. Once installed, boot up your computer and head back into the RAID configuration utility you used when you first set up your array. Choose to rebuild your array, telling the utility to duplicate the old image to your new drive so that both drives are up to speed next time you boot. The duplication may take over an hour, but when it's done your mirrored array is completely back in business.
There are several different RAID configurations beyond the basic RAID 1 mirroring, some of which offer faster hard drive performance or different combinations of performance and mirroring, so if you really like the idea of RAID you may want to explore other possibilities. That said, RAID 1 mirroring is probably the easiest RAID to set up, and it's certainly one of the least complicated and most worthwhile backup solutions on the block. Of course, you may still want to set up automated off-site backups of your really important files, which offers you an added level of backup in the event of theft. But for pure security and no-loss backups in the face of hard drive failure, nothing does the job better than a mirrored RAID 1 backup configuration.
UPDATE: As readers pointed out, RAID 1 will not safeguard you from data loss from viruses or inadvertent file overwriting, in addition to theft, as I mentioned above. The point is, automating backups of your most important files to somewhere off your RAID system, whether to another local hard drive or an off-site system, is the only way to ensure the kind of backup that keeps you safe from these issues.
So you're an expert on RAID setups? Let's hear your RAID experiences and thoughts in the comments.
Adam Pash is a senior editor for Lifehacker who tingles at the thought of live, full hard drive mirroring. His special feature Hack Attack appears every Wednesday on Lifehacker AU.