In my mission to protect the world from data loss, here’s some more tips on how to setup a data backup system. This entry is going to cover how to setup a mirrored RAID and also a RAID5. First lets go over the very basics of a RAID.

A RAID is simply a bunch of disks put together in an array, or more then 1 disk! To create a RAID, you will need more then one disk, but some RAID types support just 2 disks! The RAID types I will be talking about are the mirrored RAID or RAID and the striped RAID or RAID5.

The mirrored RAID requires a minimum of 2 hard disks. The 2nd drive mirrors the first drive so you will always have a duplicate copy of your data. Should one hard drive fail, you can take the 2nd drive and be right back where you were before the failure. You can then get a new fresh drive and set it back to mirroring. This setup is great for reliability and it’s quite easy to understand and setup.

Currently I run the mirror RAID type on my Xserve and in my desktop computer. I use 2 Lacie 160GBs on my desktop and 2 180GB internal drives on my Xserve. You can use the Disk Utility tool (located in Applications >> Utilities) to set the RAID up. You should format the drive as Mac OS Extended using the format tab and then click on the RAID tab. Give the RAID a name (whatever you want, it’s just like naming any other hard drove in your computer) and then choose Mirrored RAID Set from the RAID type drop down menu. Now drag your 2 drives into the larger box at the bottom of the window. These are the drives you will use for your RAID. Hit the create button and your RAID will be created. On your Desktop you will now see that your 2 hard drives are gone and have been replaced with one (the one is actually 2 but since it’s a RAID it will act like one drive). Each time you place a file into the RAID it will be copied onto both drives.

The next RAID type I will go over is the striped RAID or RAID5. RAID5 is great for redundancy. RAID5 requires that you have at least 3 hard drives. It’s an ideal setup for when you have a lot of files. It makes pretty good use of the disks. RAID5 will write a part of the file to each of the disks in the set. It’s gets ‘striped’ across the disks. Along with the file data it writes some parity information to the disk as well. This is done in-case any of the drives should fail you can replace the dead disk with a new one and all of that parity data can be used for rebuilding. You can use the same Disk Utility application to setup a RAID5. As before, format as Mac OS Extended. Choose Striped RAID set from the RAID type drop down menu. Drag your 3 or more drives into the box at the bottom of the window and hit the Create button! Again, you RAID set will show up on your desktop as one hard drive. Each time your drag or save a file onto the RAID, chunks of it will get written to each drive with some parity data.

RAID may sound like a very complex technology, but it’s not that bad! It’s a great way to secure your important data. While you will probably have to invest a small amount of money and time into a project like this, I think you will be impressed with it and happy to know that you’re data is safe in-case a hard drive dies or malfunction.

Standard RAID Levels
RAID Levels


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