Will enabling FileVault convert my HFS+ disk to APFS?

I have a 2017 5K iMac running Mojave 10.14.6. It has a 2 TB Fusion drive internally formatted as HFS+. FileVault is not enabled, but I wish to do so. Will the disk have its format changed to APFS if I enable FileVault?

My recollection is that the disk was originally formatted as HFS+ from the factory and when I turned on FileVault, the format changed to APFS. Granted that was over a year ago, so I could be very off-base.

I want to prevent going to APFS again. The performance degraded to dismal levels. Now that I have reformatted as HFS+, it is surprisingly speedy.

Solution 1:

FileVault and APFS are two very different things; enabling one doesn’t enable (or necessitate) enabling the other.

FileVault is encryption - it scrambles, to put it simply - the contents of your drive with a known key. Specifically, it uses a 128-bit AES encryption with a 256-bit key. See Use FileVault to encrypt the startup Disk for additional details. You can encrypt journaled HFS+ (JHFS+) formatted volumes as well as APFS volumes.

APFS (Apple File System) is simply Apple’s next generation file system. As far as encryption goes, it supports it natively unlike JHFS+.