Htydjtk

I have recently found that FileVault is disabled on my machine. Although I remember that I set "encrypt" option when I was setting the machine up.

I opened System Preferences and enabled FileVault. To my surprise it didn't take any time. I didn't have to wait while the data is encrypted. It just got instantly enabled.

How does it possible that turning on FileVault doesn't take any time?

If you have a new Mac with an SSD and T2 chip, then all data on it is encrypted always. Any election you make in FileVault just adds and removes user keys from the trust chain so that happens basically instantly.

The next time you restart, the system will notice that the first per-user key is now active and change the boot process so that the system won't unlock that storage and start the OS until your key unlocks the storage.

If I guessed wrong, we can sort out if your encryption is still being done behind the scenes by looking at diskutil output to examine any APFS and CoreStorage containers that implement the layer between the encryption on disk and the view once the volume is unlocked and mounted.

mac:~ me$ diskutil list

/dev/disk0 (internal):

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      GUID_partition_scheme                         251.0 GB   disk0

   1:                        EFI EFI                     314.6 MB   disk0s1

   2:                 Apple_APFS Container disk1         250.0 GB   disk0s2



/dev/disk1 (synthesized):

   #:                       TYPE NAME                    SIZE       IDENTIFIER

   0:      APFS Container Scheme -                      +250.0 GB   disk1

                                 Physical Store disk0s2

   1:                APFS Volume Mac                     191.7 GB   disk1s1

   2:                APFS Volume Preboot                 65.4 MB    disk1s2

   3:                APFS Volume Recovery                1.0 GB     disk1s3

   4:                APFS Volume VM                      3.2 GB     disk1s4

I didn't set "encryption" on while installing my System, but turning on Encryption with FileVault afterwards definitely takes time (about 45 min with a 512 Go SSD).

Decrypting the disk will take time with a background process as well.

You can check if your disk is encrypted or not (or in progress) through the Terminal with entering this command:

sudo fdesetup status

From your experience, it looks like enabling encryption during setup does the work, but doesn't show up in the "System Preferences" until you explicitly turn it on?