Introduced in Ubuntu 7.10 was install-time encryption support where using the alternate installer one can fully encrypt their disk in an LVM using dm-crypt. Unfortunately, the Ubiquity installer in Ubuntu 8.04 continues to lack LVM and encryption support, but using Ubuntu 8.04 Alpha 6 we have looked at the performance cost of this encrypted configuration on Ubuntu Linux. Rather than looking directly at the disk read/write overhead caused by the encryption process, we have provided some benchmarks to see how the real-world performance is impacted in both gaming and other desktop tasks.

For looking at the performance cost of Ubuntu Linux disk encryption, we had performed two clean installs of Ubuntu 8.04 Alpha 6 with the Linux 2.6.24 kernel using the alternate installer. In one installation, we had used the "Guided - use entire disk and set up LVM" method and then using "Guided - use entire disk and set up encrypted LVM." All settings in both installations were maintained the same and left at their respective default values.

Rather than just running Linux disk benchmarks, we had run a variety of our real-world tests. These Linux tests had included Enemy Territory, Doom 3, Enemy Territory: Quake Wars, LAME encoding, Gzip compression, and measuring the time to copy 364 images (amounting to 1.3GB) from a USB flash drive over to the hard drive. The tests we did for this article are as simple as that, we had ran the benchmarks on a standard LVM and encrypted LVM. The test hardware consisted of an AMD Athlon 64 X2 4200+ AM2 processor, 2GB of A-DATA DDR2-800 memory, 160GB Western Digital SATA hard drive, Abit NF-M2 nView motherboard, and a NVIDIA GeForce 6600GT 128MB graphics card with the 169.12 driver.

In the three Linux gaming benchmarks -- Enemy Territory, Doom 3, and Enemy Territory: Quake Wars -- the encrypted LVM had little impact on the frame-rate performance. In Doom 3 and ET: Quake Wars the frame-rate had dropped by just a couple frames when dm-crypt was in use. The biggest drop was with ET: Quake Wars, which equated to 2.9 frames or about a 10% drop in performance. When it came to encoding a WAV file to MP3 format with LAME and using Gzip compression on a 745MB file, the performance drop was small yet noticeable. In our last benchmark, which is the most disk intensive, which was copying 364 JPEG images amounting to 1.3GB in disk space from a Corsair Flash Voyager GT drive over to the hard drive, the performance cost of using an encrypted LVM was at about 7%.

Depending upon the situation, the performance impact of using dm-crypt will vary, but for mobile users with sensitive or just personal information, hard disk encryption is becoming a necessity and its benefits should out weigh the small performance impact. It's unfortunate that encryption support hasn't reached the Ubuntu Ubiquity LiveCD installer in time for Ubuntu 8.04 LTS, but hopefully it will be accomplished for Ubuntu 8.10. Ideally for this desktop encryption they will use Cryptsetup with LUKS support.