Replace a RAID Hard Disk in OSX Based Servers
I recently had to replace a hard disk in our OSX server at work. It had been a while since I had done this so I noted down the steps here to run through and change it. Work out which disk in your machine is faulty and replace it with a new drive.
To get started, open up terminal and run:
sh-3.2# diskutil list
This will give you a list of all the disks in your machine:
/dev/disk0
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *1.0 TB disk0
1: EFI EFI 209.7 MB disk0s1
2: Apple_HFS Macintosh HD 999.9 GB disk0s2
/dev/disk1
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *1.0 TB disk1
1: EFI EFI 209.7 MB disk1s1
2: Apple_HFS Server HD 999.3 GB disk1s2
3: Apple_Boot Recovery HD 650.0 MB disk1s3
/dev/disk2
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *2.0 TB disk2
1: EFI EFI 209.7 MB disk2s1
2: Apple_HFS Untitled 1 2.0 TB disk2s2
/dev/disk3
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *2.0 TB disk3
1: EFI EFI 209.7 MB disk3s1
2: Apple_RAID 2.0 TB disk3s2
3: Apple_Boot Boot OS X 134.2 MB disk3s3
/dev/disk4
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *2.0 TB disk4
1: EFI EFI 209.7 MB disk4s1
2: Apple_HFS TimeMachine 2.0 TB disk4s2
/dev/disk5
#: TYPE NAME SIZE IDENTIFIER
0: Apple_HFS Work *2.0 TB disk5
The new disk in this machine is /dev/disk2. We now need to work out the Unique ID for our RAID array. So we’ll run the following command so that we can get our Unique ID:
sh-3.2# diskutil appleraid list
Which will provide the following output:
AppleRAID sets (1 found)
===============================================================================
Name: 2TB Mirror
Unique ID: E07AE421-43C5-4778-B1E3-DC3365F3266B
Type: Mirror
Status: Degraded
Size: 2.0 TB (2000054943744 Bytes)
Rebuild: manual
Device Node: disk5
-------------------------------------------------------------------------------
# DevNode UUID Status Size
-------------------------------------------------------------------------------
- -none- 82D0A9C3-5ACB-4B3C-A4FC-FD473709E186 Missing/Damaged
1 disk3s2 81D8BD2A-894F-4720-8924-D4654001CF69 Online 2000054943744
===============================================================================
Next, we’ll add this disk to the existing array, the bad disk is listed in the array above as missing, because we’ve replaced it with a new disk.
sh-3.2# diskutil appleraid add member disk2 E07AE421-43C5-4778-B1E3-DC3365F3266B
This will now perform an operation to add this disk to the RAID array:
Started RAID operation on disk5 Work
Unmounting disk
Repartitioning disk2 so it can be in a RAID set
Unmounting disk
Creating the partition map
Adding disk2s2 to the RAID Set
Finished RAID operation on disk5 Work 2012+
And you’re now done for the addition of the drive. You now need to remove the old slice from the array by using this command:
sh-3.2# diskutil appleraid remove 82D0A9C3-5ACB-4B3C-A4FC-FD473709E186 E07AE421-43C5-4778-B1E3-DC3365F3266B
You can now check that your RAID looks good by running:
sh-3.2# diskutil appleraid list
The RAID status should now be showing as online.