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I would like to create a Fusion Drive from my SSD and HDD both installed inside my MacBook Pro 15" Mid 2012. I've read an article online which said that in order to do that, I'd need to boot Mavericks from an external USB drive. So I've picked a 64 GB USB stick and partitioned it in two, 8 GB for the installer and the rest for the operating system to install to. I've managed to create the USB installer of Mavericks using Unibeast, the installer boots without any problem, it installs normally but when I reboot I get a stop sign with a spinning wheel under it. How can I solve this problem?

The tutorial I'm trying to follow to create the Fusion drive is this one: Manually Create an Apple Fusion Drive on Mountain Lion/Mavericks/Yosemite


I need to create a Fusion drive from the 2 internal drives (240GB SSD and 1TB HDD). On the SSD I already have installed El Capitain and I used the HDD to store files. Now I've seen that you can merge this two in a single LogicalVolume and OS X will see it as if it were a Fusion Drive.

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You do not need Unibeast (a tool for hackintoshes) to create an external installer. Can you confirm you're only using it to run the createinstallmedia command provided by apple as per this page?

Apart from that it seems you are confusing an external Mavericks installation with an external Mavericks installer. All you should have to do is double click the installer, straight from the App Store still laying in /Applications on your internal drive, then pick the external volume as a target (wipe the current ones and make a new one for the entire stick). Using all-apple tools should make that go smooth.

Then just boot from the external stick by holding down opt at boot, and complete the guide.

When in doubt or in need in help, always boot in verbose mode to get more information, and above all, do not over complicate things.

  • Thank for your answer, yes i'm trying to run that command. I used Unibeast because when I try to run the mavericks app on my MacBook, I get an error that says that the app is too old to be run. Anyway I can get through this error? Are you suggesting to complete the guide from the installer? – Daniele C Apr 12 '16 at 12:26
  • True, forgot about that. Yes, run createinstallmedia, keep the rest of the stick clean, then once booted from it (this is probably where things have gone wrong) format the rest of the space on your stick from within the installer to make sure it's set up properly for Mavericks including EFI and recovery partitions. – tolgraven Apr 12 '16 at 13:13
  • Ok i'll try it later. So I should run createinstallmedia from within the Mavericks installer in order to create the Fusion Drive right? Or did I missunderstand? – Daniele C Apr 12 '16 at 13:37
  • createinstallmedia is for creating the Mavericks installer, that command is run from your regular current install. If you can confirm that's all Unibeast did then you can just use the one you already have. Just make sure to enter disk utility and format the rest of your stick while booted from the installer, before you go ahead and run the installation. – tolgraven Apr 12 '16 at 13:50
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    I've managed to do it from the installer. I was getting an error that i fixed by erasing both disks from disk utility. I didn't do it before because I wanted to do it from the command line... anyway thanks for the help. It is also the first time I've used Time Machine and i'm really impressed, it restored EVERYTHING! – Daniele C Apr 15 '16 at 9:40
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You can't simply create a DIY-Fusion Drive with already existing partitions containing a system and data while preserving the data on both.

You either loose both partitions (using the linked guide) or at least one using an undocumented diskutil command.

  1. diskutil cs create ...

    If you create your Fusion Drive with diskutil coreStorage create myLogicalVolGroup /dev/disk0(s2) /dev/disk1(s2) and diskutil coreStorage createVolume lvUUID jhfs+ "name" 100% both partitions (disk0s2 and disk1s2) will be erased and all data is lost.

  2. diskutil cs convert ...

    An undocumented feature is the diskutil cs addDisk .... After converting one volume with diskutil cs convert /dev/disk0s2 to a CoreStorage Logical Volume Group and CoreStorage Logical Volume you may add a second Physical Volume to the existing LVG and later expand the LV to the full size. The content of the converted will survive, the content of the added PV will be erased.

    To add a 2nd PV enter first diskutil list and diskutil cs list to get an overview. Now add a PV with diskutil cs addDisk lvgUUID /dev/diskXsY to the existing LVG (with diskXsY: the disk identifier of the partition to add and lvgUUID: the UUID of the Logical Volume Group). Then expand diskutil cs resizeVolume lvUUID 100% (with lvUUID: the UUID of the Logical Volume).

    The addDisk/resizeVolume commands often fail with some obscure errors.


To preserve all data back it up and then use a the mentioned guide!

  • Thank you for your answer, no i don't care to keep the data. I've done a time machine backup already. I will try – Daniele C Apr 12 '16 at 17:13

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