When Yosemite was released in October 2014, one of the changes it introduced was including a new FileVault 2 enablement option in Apple’s Setup Assistant. This option encouraged new users of Yosemite to enable FileVault 2 encryption and had the choice to enable FileVault 2 selected by default.
When the encryption process began, a significant issue then appeared for a number of users where the Mac would report Encryption paused during the encryption process, then never resume the encryption process.
This produced a situation where the Mac could not complete encryption, but would not decrypt either because the encryption process had not completed. The only fix appeared to be deleting the existing CoreStorage volume, which addressed the issue at the cost of deleting everything stored on the boot drive.
Fortunately, OS X 10.10.3 includes a fix that should stop this issue from occurring on OS X 10.10.3 and later. There is also now a procedure that should fix Macs still affected by this problem. For more details, see below the jump.
The root cause for the encryption pausing and not resuming was a problem with resizing the CoreStorage volume. When the CoreStorage volume was unable to grow, the encryption was paused and could not resume until the resize issue was addressed.
To fix this issue:
1. Update your Mac to 10.10.3, or boot from an alternate drive which is running 10.10.3.
2. Unlock the encrypted drive if necessary
3. Open Terminal
4. Run the following command to get the disk identifier for the boot drive:
diskutil list
5. Once you have the disk identifier information, run the following command with root privileges:
fsck_cs -y disk_identifier_goes_here
Running the fsck_cs tool should repair the CoreStorage volume and address the resizing issue. As part of the output, it should show that encryption is resuming.
