But FWIW, drives are not <i>that</i> slow.  On my i7 machine, a <i>really</i> fast machine, the disks (one SSD, one RAID-1 array with 2 normal disks) can read data much faster than the blocks can be decrypted.  My read speed is limited to about 60MB/s compared to the 130MB/s that the disks can actually read.  (Yeah, kcryptd is single-threaded.  Ouch.)<p>It's even worse on my Atom laptop.  The SSD can do about 150MB/s (as I accidentally bought a really nice one), but the tiny CPU can only manage to decrypt about 20MB a second.  And on a laptop, crypto is not exactly paranoia; it's the only sane thing to do.