[dm-crypt] ext3/ext4 full disc encryption performance

DZ sc13nc3d at gmail.com
Wed Feb 3 15:55:12 CET 2010


I've been using full disk encryption with luks on two laptops for
about 2.5 years. One is 64 bit Fedora (upgraded to 12), another is 32
bit Ubuntu (upgraded to 9.10), both were ext3, until recently.

I noticed that over time, performance degraded substantially,
especially on Fedora, which was put to a heavier use. The laptop has 4
Gb RAM and two 2.5 GHz T9300 CPUs.

It was especially unbearable after a reboot. Programs like firefox and
thunderbird would take close to a minute to start when ran for the
first time after a boot. The boot process was painfully slow, and some
Gnome applets (e.g. Tomboy notes, keyboard layout switcher) would fail
to load on the first login. I experienced this problem on both
laptops.

I also use 3 desktops with no encryption and a netbook with ecryptfs
on /home, which work fine. All are Dell. The Gnome applets problem
seems to be due to slowness of the full disk encryption.

I had to log out and relogin to make the applets appear. I tried
various boot and mount options and was thinking about switching to
ecryptfs (encrypted home).

The last thing I tried is to migrate ext3 to ext4.  I also converted
/home, /usr, /opt to extents, following
http://www.debian-administration.org/article/Migrating_a_live_system_from_ext3_to_ext4_filesystem

That seemed to do the trick. Gnome applets now load fine on both
laptops, and startup time is back to snappy.

Is this a typical experience: ext3 performance degradation with time
and a much better performance with full disk encryption once ext3 is
migrated ext4?



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