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I want to ask you how can I get back together my Fusion Drive (merge HDD and SSD together). I was installing Windows 10 and during installation it crashed and I was not able to boot in Windows neither OS X. I also lost recovery partition, so I am going to install it with internet recovery or with my installed OS X on my external HDD. Thanks for any advice

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Preparation:

  • Detach any external drive (especially your external Time Machine backup drive)
  • Restart to Internet Recovery Mode by pressing alt cmd R at startup.
    The prerequisites are the latest firmware update installed, either ethernet or WLAN (WPA/WPA2) and a router with DHCP activated.
    On a 50 Mbps-line it takes about 4 min (presenting a small animated globe) to boot into a recovery netboot image which usually is loaded from an apple/akamai server.

    I recommend ethernet because it's more reliable. If you are restricted to WIFI and the boot process fails, just restart your Mac until you succeed booting.

    Alternatively you may start from a bootable installer thumb drive (preferably Yosemite or El Capitan) or a thumb drive containing a full system (preferably Yosemite or El Capitan).

Rebuild Fusion Drive

All data on the disks will be deleted.

  • Booted to Internet Recovery Mode open Utilities → Terminal in the menubar and enter:
    diskutil cs list to get a CoreStorage listing.
  • Copy the Logical Volume UUIDs one by one, if any are listed.
  • Now delete all Logical Volumes with diskutil cs deleteVolume LVUUID.
  • Copy the Logical Volume Group UUID, if any is listed. It's the first listed in the listing of diskutil cs list.
  • Then delete the Logical Volume Group with diskutil cs delete LVGUUID.
  • Enter exit and quit Terminal
  • Open Disk Utility. Enter 'Ignore' if you are asked to fix the drives.
  • Choose your SSD and erase it: 1 Partition Mac OS X Extended (Journaled), GUID Partiton table and hit Erase.
    Please check that the size is ~121 GB

    Example:

    ssd

  • Choose your HDD and erase it: 1 Partition Mac OS X Extended (Journaled), GUID Partiton table and hit Erase.
    Please check that the size is ~2 TB

    Example:

    hdd

  • Quit Disk Utility and open Terminal

  • Enter diskutil list

    Example (your disk identifiers and sizes are different of course: Your volume SSD probably has the Identifier disk0s2 and the size 121 GB and your volume HDD probably has the Identifier disk1s2 and the size 2.0 TB):

    diskutil

  • Enter diskutil cs create "Name" IdentifierSSD IdentifierHDD
    In your case probably diskutil cs create "Macintosh HD" disk0s2 disk1s2.

    Copy the resulting LVGUUID

    Example:

    cscreate

  • Enter diskutil cs CreateVolume LVGUUID jhfs+ "Macintosh HD" 100%.

    Example:

    lvcreate

  • Enter diskutil cs list
    Check the size of your Logical Volume. It should have the size ~1.121 TB

  • Quit Terminal

  • Open Disk Utility and check your newly created volume for errors
  • Quit Disk Utility
  • Open Restore OS X. Install and configure OS X. The original OS X your Mac came with will be installed.
  • After configuring OS X, download the newest available system installer with App Store and upgrade your system.
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Are you using Bootcamp or a Windows VM (aka Parallels) ? You can use the SSD as the boot drive for the applications and create a partition on the primary HD.

  • I used to have on VM but then I tried Bootcamp and this have happened. So now I just want the factory settings, so I want to merge drives back together as they were before with original Fusion drive. – Polino Dec 25 '15 at 13:01

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