Half of my disk is full with a partition "update" (incl. solution)

I just discovered that exactly half of my disk is occupied by a partition called "update" … I think I know why and wanted to share the knowledge as loads of other had the same problem but no answer.

I think the reason is that the disk is ENCRYPTED. Encryption is nice from a safety standpoint, but horrible in terms of file handling: space from the erased files only gets freed up after a restart, if your disk's file system becomes corrupted and you need to rescue files, you're DOMMED and during a system update, up to half the space is used for the update, e.g. in case a new Os uses a new file system that isn't compatible with previous ones. So that's why half of your disk space is reserved for an update.

In my opinion, the far better solution is:

1) turn encryption off (note that this will also copy your whole disk into the unencrypted part of the disk – that's why in old Os version, you sometimes couldn't turn encryption off, EVER, since you didn't have the extra space).

2) Open Utilities -> Disk Utilities

3) click File -> new image -> blank image

4) Create a new disk image with the selections below (ensure that it's big enough for everything you need to keep really, really secret, like contracts, pictures or whatever)

5) you now have an encrypted disk image that can be transferred to other media, but is encrypted with a 256-bit key and can only be opened by a password, while the rest of your disk is accessible and repairable.

Note that you can also use this encrypted sparse disk image for time machine backups on corporate servers that don't even support the Apple File System … your disk image just has to be several hundred GB in size to accommodate your backups and has to be mounted manually before you do your backup.