I did a small performance test yesterday and was very surprised by the results. I wanted to see which encrypted filesystem was faster between Truecrypt and LUKS. I created 2 20-gig files, one with Truecrypt and the other with LUKS encryption. Then I mounted the encrypted files and copied a 180 meg file 10 times, synced, and then reported the time taken. Here’s the results:

Truecrypt test:

time (for f in $(seq 1 10); do; cp bigfile truecrypt-mnt/bigfile-$f; done;)
0.22s user 26.30s system 15% cpu 2:47.06 total

LUKS test:

time (for f in $(seq 1 10); do; cp bigfile luks-mnt/bigfile-$f; done;)
0.20s user 8.40s system 15% cpu 55.169 total

Wow. Now, granted, this is a simple enough test, but does anyone have any ideas why LUKS would be 3 times faster in writing 1.8 Gigs than Truecrypt?