Performance Overhead of Encrypted /home
- by SabreWolfy
I have a netbook with Windows on the second partition and Xubuntu (/ and /home) on the third partition. I selected to encrypt my home folder during installation. The performance of the netbook is adequate for the small machine that it is, but I'm looking to improve performance. I could not find much information about the overhead (CPU or drive) associated with home partition encryption. I ran the following, writing to my home partition as well as the the mounted Windows partition:
dd if=/dev/zero of=~/dummy bs=512 count=10240
dd if=/dev/zero of=/media/Windows/dummy bs=512 count=10240
The first returned 2.4MB/s and the second returned 2.5MB/s. Can I therefore deduce that there is very little overhead to home folder encryption? I'm not sure if the different filesystems will make any difference (/ and /home are ext3).
Update 1
I don't know why I didn't use /tmp instead of the mounted Windows folder. Only /home is encrypted, so /tmp is unencrypted ext3. The results of the dd as above are astounding:
~: 2.4 MB/s
/tmp: 42.6 MB/s
Comments please? The reason I am asking this is that disk access on the netbook is noticeably slow.
Update 2
I timed each of the dd operations with time:
~:
real 0m2.217s
user 0m0.028s
sys 0m2.176s
/tmp:
real 0m0.152s
user 0m0.012s
sys 0m0.136s
See also: discussion on UbuntuForums.org and bug report
Edit: Output of mount:
/dev/sda3 on / type ext3 (rw,noatime,errors=remount-ro,user_xattr,commit=600)
proc on /proc type proc (rw,noexec,nosuid,nodev)
none on /sys type sysfs (rw,noexec,nosuid,nodev)
fusectl on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
none on /dev type devtmpfs (rw,mode=0755)
none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
none on /dev/shm type tmpfs (rw,nosuid,nodev)
none on /var/run type tmpfs (rw,nosuid,mode=0755)
none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
gvfs-fuse-daemon on /home/USER/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=USER)
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