Time Machine encryption versus disk encryption

Question

I'm backing up with Time Machine on a Mac Pro to an internal hard drive. I have encrypted my Time Machine backup in system preferences. This resulted in an initial backup of about 2 days, and backups are now slower than they were when unencrypted. A glance at the Time Machine menu bar item often shows the status "Encrypting Backup Disk... (X %)" Presumably it is encrypting more space to allow for the impending backup as the entire drive isn't pre-encrypted.

I have encrypted other internal drives by right clicking and choosing encrypt. It seems that wiping my Time Machine hard drive, encrypting the drive and then doing non encrypted Time Machine backups would protect the data just as well, and offer faster backups. Would encrypting the drive itself prevent restoring from the backup or are there any other drawbacks?

Answer 1

Encrypting the drive itself would probably be okay -- you'd just have to unlock the drive/partition before Time Machine would be able to access it.

Honestly, though, you asked Mac OS to use an encrypted backup, and encryption takes extra time.... so... just let it do its thing and let it keep your data safe. If you have files that are too large and modified too often to be backed-up efficiently using Time Machine to the encrypted disk, consider making special arrangements for those files (and exclude them from TM) so they don't bog-down your TM backup process.

Answer 2

It seems like if one selects an unencrypted disk and choose "Encrypt backup" afterwards via TM menu it assumes that disk has some files (maybe from previous TM backups or other stuff) and goes through every disk block to encrypt it and keep those files. On the other hand if the disk has been pre-encrypted it doesn't have to do that and skips that step. Don't know for sure though, only guessing.