Partitioning mirrored disks under Mac OS X / Server

Yes it's possible! (although Disk Utility says it's not!

Become root (or put sudo before the commands)
Make the RAID:
```
diskutil createRAID mirror MyRAIDSet HFS+ disk1 disk2
```
Or via the GUI, using Disk Utility.app if you like. A new HFS+ filesystem will be created there and will attach as a new disk, like /dev/disk3. Yes its nice, but this is what we don't need.
Unmount the new disk with diskutil unmount disk3. Do not eject it!
Partition the disk as you like:
```
diskutil partitionDisk disk3 2 HFS+ Part1 10G HFS+ Part2 10G
```
See diskutil's partitionDisk output for examples. There's no GUI way, that's why you reading this! A partition map and yours partitions will be created and will have a new fs created and mounted (as /dev/disk3s2 and /dev/disk3s3 in my example).

Yes! That's it! Easy?

I'v tried this on PMG4 using two 6GB HDD's and running Mac OS X Server (10.2 & 10.2.8). Then on an XServe with two 180GB IBM's (why Apple is still using these?) Works great. Disk Utitilty.app sees the RAID, can check it, but it has no clue about the volumes on it. So you have to fsck manually. When journaling is turned on, this is probably not needed. Turn on journaling using diskutil enableJournal /Volumes/Part1. Thats all for now. Have fun!

# diskutil createRAID mirror testraid0 HFS+ disk5s2 disk6s3 Timed out waiting for arbitration Failed to find IOMedia for disk5s2. Header didn't completly write out! An error occured attempting to create the raid set #

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The following comments are owned by whomever posted them. This site is not responsible for what they say.

Partitioning mirrored disks under Mac OS X / Server
Authored by: diamondsw on Thu, Oct 30 2003 at 12:02PM PST

Can't you just mirror the partitions individually?

Partitioning mirrored disks under Mac OS X / Server
Authored by: spaceboy.cz on Sun, Nov 16 2003 at 2:50PM PST

How would You do that?

Partitioning mirrored disks under Mac OS X / Server
Authored by: dkg on Mon, Feb 16 2004 at 11:53PM PST

it would be nice to just mirror the partitions individually, like you say. Unfortunately, apple's diskutil software RAID doesn't look like it allows you to do RAID over partitions, just on disks. See this post to the macosx-admin list for details.

if there's been any change in diskutil's ability to do this since that posting, i haven't been able to find any documentation which describes the change. and (at least as of jaguar today with all the latest patches) trying to do diskutil createRAID on two partitions fails with the same error as mentioned in the link above:

Partitioning mirrored disks under Mac OS X / Server
Authored by: Frederico on Mon, Dec 15 2003 at 5:07PM PST

Any way to make this bootable?

root partition
Authored by: suarezry on Fri, Dec 19 2003 at 1:08PM PST

How do you partition the mirror set if it's the root partition?

Partitioning mirrored disks under Mac OS X / Server
Authored by: astafford on Tue, Jan 20 2004 at 11:33AM PST

I tried this for a stripe set. It seems to work at first but I can not boot from the disk. Performance is not good either except for uncached 4 k byte writes ( 200 xbench ) others are about 60.
Disktools does not work on the drive as expected, neither do Norton DiskDoctor or Speedisk.

Alan

Partitioning mirrored disks under Mac OS X / Server
Authored by: astafford on Tue, Jan 20 2004 at 11:37AM PST

PS Using firewire disks.

Partitioning mirrored disks under Mac OS X / Server
Authored by: jelockwood on Wed, Jan 25 2006 at 12:27PM PST

The post from Spaceboy was useful. Unfortunately it appears this approach no longer work with Mac OS X 10.4

Any chance someone has found a new method?

Note: I tried it first under 10.4.4 (unsuccessfully) and then 10.3.9 (successfully) using the same disks each time.

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