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Create a Fusion Drive with a Recovery Partition
Authored by: ila225 on Apr 23, '14 10:19:05AM

It also depends on which version of the OS you're using to make the fusion drive AND the age of the Mac you're running.

I don't know exactly if it is only in Mavericks of if Mountain Lion already supported this in the latest updates, but after creating a Fusion Drive the second hard drive actually contains a recovery partition.

For example, this is my FD:

$ diskutil list
/dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *256.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage                         197.9 GB   disk0s2
   3:                 Apple_Boot Boot OS X               134.2 MB   disk0s3
/dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk1
   1:                        EFI EFI                     209.7 MB   disk1s1
   2:          Apple_CoreStorage                         892.0 GB   disk1s2
   3:                 Apple_Boot Boot OS X               650.0 MB   disk1s3
/dev/disk2
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS Mac OS X               *1.1 TB     disk2

*don't mind the disk size as there are windows partitions I removed from the listing

But what you want to pay attention to is the size of both "Boot OS X" partitions. On the first disk, it is 134 Mb, on the second, it is 650 Mb.

Digging inside the second partition one will find the BaseSystem.dmg hidden from Finder, but visible through Terminal's ls command:

$ diskutil mount disk1s3
Volume Boot OS X on disk1s3 mounted
$ ls -lha /Volumes/Boot\ OS\ X/com.apple.recovery.boot/
total 972776
drwxr-xr-x  11 root  wheel   374B Jan 29 18:07 .
drwxr-xr-x  12 root  wheel   476B Apr 22 22:01 ..
-rw-r--r--@  1 root  wheel   809B Jan 29 18:07 .disk_label
-rw-r--r--@  1 root  wheel   3.2K Jan 29 18:07 .disk_label_2x
-rw-r--r--@  1 root  wheel   1.9K Oct 16  2013 BaseSystem.chunklist
-rw-r--r--@  1 root  wheel   459M Oct 16  2013 BaseSystem.dmg
-rw-r--r--   1 root  wheel   4.2K Aug 24  2013 PlatformSupport.plist
-r--r--r--   1 root  wheel   475B Oct 16  2013 SystemVersion.plist
-rw-r--r--   1 root  wheel   494K Jan 29 18:07 boot.efi
-rw-r--r--   1 root  wheel   361B Jan 29 18:07 com.apple.Boot.plist
-rw-r--r--   1 root  wheel    16M Oct 16  2013 kernelcache

Trying this on an iMac 27" late 2009, the Recovery Partition does NOT show up when holding the Option key. It is good to mention that the iMac late 2009 was built BEFORE Fusion Drives, thus leading me to conclude that part of its BIOS / UEFI system simply doesn't know to look for that particular recovery partition aside the standard one mentioned on the article.

It DOES show up on newer macs that were built AFTER Fusion Drive was available.

I hope this helps a bit. =)

Edited on Apr 23, '14 10:19:36AM by ila225


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Create a Fusion Drive with a Recovery Partition
Authored by: cpragman on Apr 25, '14 06:05:37PM

@ila225 -
You didn't mention what OS you had this issue with. Fusion drives are allegedly supported on 10.8.3 and higher.
If you have 10.8.3 or greater, you can try booting from your temporary clone, and running the OSX Installer. Install a fresh copy of OSX on the original Internal HD. This should create a working OS on "Macintosh HD", and will also create the "Recovery HD" and "Boot_EFI" partitions. After doing that, create the fusion drive using the diskutil core storage commands (join the "Macintosh HD" partition and the SSD together, leaving the Boot_EFI and Recovery Partition undisturbed.

I've actually had to do this a few times myself.



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