This document will cover some of the most frequently asked questions about imaging a Mac device with Fusion Drive technology enabled.
What is a Fusion Drive?
A Fusion Drive is two logical volumes that have been tied together, using MacOS's CoreStorage functionality, to appear to the operating system as a single drive. When you purchase a Mac equipped with a Fusion Drive it will have a Solid State Disk and a Hard Disk Drive that have been "fused" together to act as a single drive. Files and Programs that are used most frequently are automatically moved onto the SSD to enable faster load time for those files. Files less commonly used with reside on the HDD. It is Apple's implementation of a hybrid drive. With this technology devices actively manage their file system to ensure faster access to the most commonly used files and features of that particular device.
What can be a Fusion Drive?
A Fusion Drive is not limited to the configuration from the factory, it can also be configured using external drives, USB drives, and even multiple HDD disks. A Solid State Disk is not required to build a Fusion Drive. It is, however, uncommon to fuse other types of disks together except in special cases. Fusion Drives do rely on the CoreStorage functionality of the MacOS to function properly.
How do I image a Fusion Drive?
Just like you would any other disk. The caveat is that you need to ensure you are telling the image deployment tool to apply the image to the correct volume. This is most easily done by confirming from a terminal prompt while inside of the NetInstall environment which volume to direct the image to. If you need to do this inside of Ivanti Endpoint Manager please refer to this document: How To: Troubleshoot Mac Provisioning
Normally I have to disable CoreStorage, should I still do that?
If you disable CoreStorage while working with Fusion Drives, it will simply break up the disks that are fused together and you will have to rebuild the Fusion Drive before you can image the device retaining the Fusion Drive functionality.
Should I tear down and rebuild the Fusion Drive?
It is not necessary.
If the Fusion Drive is already configured you can leave it intact and proceed with formatting the volume and deploying the image to the disk as normal. If you suspect there is a problem with the Fusion Drive itself you can rebuild it either manually or using the actions built into Ivanti Mac Provisioning to handle this operation.