How to Create a Software RAID on a Lion Server
For Macs with multiple hard drives running OS X Lion Server, Disk Utility can set up multiple drives to work together as a software RAID to increase performance, protect data, or both.
Software RAID takes some of the computer’s processing power, and it isn’t as secure as a hardware RAID controller system. For example, a system crash could affect a software RAID but would not affect a hardware RAID. However, a software RAID is far less expensive and does provide the benefits of data redundancy. You can also use external FireWire drives in a RAID set.
Here’s how to create a software RAID:
Launch Disk Utility.
Click the RAID tab.
Drag and drop drives from the left pane into the RAID pane.
Use drives — not volumes — from the left pane. Partitions/volumes are listed under the drive name and are indented.
Type a name for the RAID set in the Name field.
In the Format pop-up menu, make sure that Mac OS X Extended (Journaled) is selected.
From the RAID Type pop-up menu, choose Mirrored, Striped, or Concatenated:
Mirrored (or RAID 1) writes the same data to two drives simultaneously. If one drive fails, the other drive still contains all the data.
Striped (or RAID 0) makes multiple hard drives of the same size work together as a single, fast, large hard drive. Data from a file is fragmented and written on multiple drives. When accessing the file, the system reads the fragments from all the drives simultaneously. If one of the drives in a RAID 0 fails, all the data is lost.
Concatenated combines multiple hard drives into one without the speed benefits of striping, but you can combine drives of different sizes. Concatenating gets really interesting when used with another RAID. For example, concatenate two FireWire drives that add up to the capacity of the internal drive and then mirror the internal drive with the concatenated FireWire drives.
You can also use it to create a RAID 1+0. For example, if you have four drives, concatenate a 2-drive mirror array with a 2-drive striped array. This gives you the performance of striping with the redundancy of mirroring.
Click the Create button.