[dm-crypt] Hybrid drives

Mikko Rauhala mjrauhal at cc.helsinki.fi
Sat Jul 17 13:05:48 CEST 2010


la, 2010-07-17 kello 11:46 +0200, Heinz Diehl kirjoitti:
> As far as I understand, the SSD part of these hybrid drives is used as a
> cache, which doesn't loose its data when powered off.

Correct, but the same of course applies for the disk itself.

It doesn't magically cache the computer's unencrypted memory, merely
what's written on the disk. If that includes unencrypted encryption
keys, you'd have the same problem without said cache.

The most the SSD cache can do to harm you is to perhaps have leftover
overwritten old data that wouldn't otherwise exist on the drive anymore.
But with proper use of dm-crypt, any such leftovers would be encrypted
along with the rest of it.

> When you format the disc using "cryptsetup luksFormat", the 4 GB SSD part
> isn't included. Please correct me if I'm wrong.

You're wrong in a very confused way. The SSD never stores anything that
wasn't on the hard disk, and only a part of that anyway. All operations
on the disk likewise indirectly affect the SSD cache.

-- 
Mikko Rauhala <mjr at iki.fi>       - http://www.iki.fi/mjr/blog/  
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