How to create a mirror software RAID with two partitions with OSX
With the OS X Disk Utility it is very easy to manage your different hard disks. It also allows you to create a software RAID in the modes 0 ( striping ) and 1 ( mirroring ).
In most cases you don’t want the complete hard drive to be part of the RAID but want to seperate the disk into multiple partitions. To create those multiple partitions each in a RAID you could use the following steps.
In case you have two new (physical) hard drives and want to create two partitions where each of those partitions is mirrored onto the other drive, do the following steps:
- Create all partitions on each of the hard drives. So two partitions on the first hard drive and two partitions of the same size on the second drive.
- Mark the first partition on the first drive and press the RAID button to start the creation of the first RAID. Drap and Drop both partitions into the RAID list in the middle. Give it a name, select the RAID type and the filesystem format.
- After the creation of the first RAID is complete, unmount the new RAID disk in the Disk Utility. The used disk partitions should now be grey and should not allow further actions. When i didn’t unmount the RAID disk i still got an POSIX error – Disk still in use.
- Do the same steps for the second RAID combination. After the second RAID is completed mount the first RAID system again.