Mavericks/Yosemite Dual-Boot on a DIY fusion drive

As OS X 10.10 Yosemite DP1 runs awful in a virtual machine I wanted to install it onto my MacBook as a dual-boot configuration with OS X 10.9 Mavericks. My MacBook runs on a self-made FusionDrive configuration using a SSD and a regular hard disk. Here is a link to a HowTo for that FusionDrive stuff. As Mavericks is already installed, the hard part was to create partition for the Yosemite installation. What absolutely is not working is:

  • Simple create two volumes on the FusionDrive using the „diskutil coreStorage createVolume“ command
  • Add a second partition using the disc-utility

The disc utility does create a partition, but it completely ignores the size you specified. For me it worked by booting from USB and using the „resizeStack“ command (I got that hint from here).

diskutil cs resizeStack X Y 991G jhfs+ Media 120G

This command will resize the FusionDrive volume to 991G while creating a second partition with the size of 120GB. To exactly know how big your partitions should be, type:

diskutil cs list

It will show you the size of the current volume. If its, for example, 1000GB and you want to create a 20GB second partition, type:

diskutil cs resizeStack X Y 980G jhfs+ partitionname 20G

X should be the UID from the volume you want to shrink (also called Logical Volume (not Family)). Y is the UID from the physical volume you want to create the 2nd partition on. I used my regular disk for that to avoid reducing the performance of my FusionDrive. To make it clear: The second partition will not be part of the FusionDrive, so the performance may be slower that used to. To display the UIDs use the list command:

diskutil cs list

After that, install Yosemite on the newly created partition. After a successfull installation, you can choose which system to boot by holding the alt-key on boot. Worked for me and I hope it will work on your setup, too 😉

OS X Yosemite 10.10 in Virtual Box

I finally managed it to install Yosemite in VirtualBox as a, well, virtual machine.

Create a new virtual machine, choose OS X 10.9 x64 as operating system and give it some RAM. Then you need to prepare the install disk image (i have used the developer preview version!) with the following steps (taken from here):

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iesd -i /Applications/Install\ OS\ X\ 10.10\ Developer\ Preview.app -o yosemite.dmg -t BaseSystem
hdiutil convert yosemite.dmg -format UDSP -o yosemite.sparseimage
hdiutil mount /Applications/Install\ OS\ X\ 10.10\ Developer\ Preview.app/Contents/SharedSupport/InstallESD.dmg
hdiutil mount yosemite.sparseimage
cp /Volumes/OS\ X\ Install\ ESD/BaseSystem.* /Volumes/OS\ X\ Base\ System/
hdiutil unmount /Volumes/OS\ X\ Install\ ESD/
hdiutil unmount /Volumes/OS\ X\ Base\ System/
hdiutil convert yosemite.sparseimage -format UDZO -o yosemitefixed.dmg

You can save these commands as a bash script, run it and relax. When finished, mount the yosemitefixed.dmg as a live-CD in your virtual machine. Internet said it is a good idea to change the chipset of the virtual machine to PIIX3, so do that. After installation it is important to remove the live-CD image and reboot. Voila, should work. Good luck!

But performance is really bad at the moment.