Operating systems

I got a new iMac and wanted to use an USB-drive as Time Machine backup destination for it. When it comes to easily movable backup-drives, my policy is to encrypt them. If a drive is lost/stolen/misplaced, other people don't get to access my data.

When OS X sees an empty USB-drive, and there is no Time Machin already set up, it asks if you'd like to use the newly found drive as Time Machine backup destination, which is nice and user friendly. During Time Machine setup, there is a checkbox "Encrypt drive". I checked it, but whatwhatwhat?! It refused to work. Error message:

There was an error preparing the Time Machine backup disk "TimeMachine" and an additional explanation: The given file system is not supported on Core Storage.

Well... that's strange. I have no idea what a Core Storage is, or why an Apple formatted HFS+ partition would not be a valid (encrypted) backup destination.

Here is what I did. My drive was already formatted when I got it:

$ diskutil list disk3
/dev/disk3
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk3
   1:                        EFI                         209.7 MB   disk3s1
   2:       Microsoft Basic Data WD Backup               1000.0 GB  disk3s2

There is a 1 TiB Western Digital drive with a NTFS-partition on it. So I had to delete the partition and create a better suitable one:

$ diskutil partitionDisk disk3 1 GPT HFS+ TimeMachine 1T
Started partitioning on disk3
Unmounting disk
Creating the partition map
Waiting for the disks to reappear
Formatting disk3s2 as Mac OS Extended with name TimeMachine
Initialized /dev/rdisk3s2 as a 931 GB HFS Plus volume
Mounting disk
Finished partitioning on disk3
/dev/disk3
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk3
   1:                        EFI                         209.7 MB   disk3s1
   2:                  Apple_HFS TimeMachine             999.9 GB   disk3s2

This is the partition setup that refuses to work.

After couple of hours of Googling I found the solution:

$ diskutil enableJournal disk3s2
Journaling has been enabled for volume TimeMachine on disk3s2

I seem to have misplaced the links already. Sorry. Anyway, the problem was that I didn't enable journaling on the partition. I can understand why that is a requirement for Time Machine. Having a journaled partition adds robustness to write operations. The real questions are:

• Why creating a HFS+ partition does not enable journaling automatically?
• On Linux creating EXT2 or EXT3 partition does not enable journaling automatically
• On Linux creating EXT4 journaling is enabled by default
• Why doesn't Time Machine state the reason?
• Saying that Core Storage is not supported is a bit vague!