Adding dm-cache to existing crypt device?

[Stefan Klein <st.fankl.in@xxxxxxxxx>]

Hi,

on my laptop I encrypted sda1 (HDD) using luks, the crypted device is then used as a lvm physical volume.

Now I got an additional SSD and want to setup dm-cache.

I see 3 possible configurations:

1. Encrypt the cache and add caching for each logical volume. I would get control about which volumes are cached but the setup feels kind of wrong since the data is encrypted twice.

2. Add the caching layer on top of sda1 and use the resulting cached block device as encrypted device. That way the whole physical volume would be cached, I don't have control which volumes are cached but once it's running it seams to be the simpler setup.

3. Redo the complete setup, using lvm directly on the hardware and add (optional) caching and (optional) encryption to the volumes.

(I read the FAQ, especially 2.2 about LVM, but it's just very handy if you deal with short living virtual machines)

For option 2, the added caching layer should be transparent to cryptsetup/Luks, so i should just have to tell it to use the cached device instead the old one, anybody done this before?

Am I missing something?

Thank you,

Stefan

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