Usually this is only in the form of a header on the block device. Dm-crypt on linux has a mode called 'plain'. This uses the sector number and passphrase/keyfil

Usually this is only in the form of a header on the block device. Dm-crypt on linux has a mode called 'plain'. This uses the sector number and passphrase/keyfile to generate a unique encryption key for each sector. This means there is no meta-data, and corruption of any physical sectors map directly to the unencrypted block device. In this case, it does look just like random data.