encfs/PERFORMANCE.md

EncFS Performance

EncFS runs in user-space while eCryptfs runs in the kernel. This is why it is often assumed that eCryptfs is faster than EncFS. To compare the actual performance of EncFS and eCryptfs on top of different backing disks, the EncFS test suite contains an automated performance test - benchmark.pl.

performance.pl takes care of setting up EncFS and eCryptfs mounts, clearing caches and syncing disks between the tests, and also to unmount and clean up everything in the end.

It performance the following tests:

• stream_write: Write 100MB of zeros in 4KB blocks
• extract: Extract the linux-3.0.tar.gz archive
• du: Disk space used after extraction, in megabytes
• rsync: Do an "rsync -an" of the extracted files. This simulates an rsync to a destination that is (almost) up-to-date. The workload consists mostly of stat() calls.
• delete: Recursively delete the extracted files

For EncFS, the default options are used. This means:

• AES with 192 bit key
• Filename encryption

For eCryptfs, the options used are

• AES with 128 bit key
• Filename encryption

For all the details, take a look at benchmark.pl .

Results

The performance of an overlay filesystem depends a lot on the performance of the backing disk. This is why I have tested three different kinds of disk:

• Classic HDD: Seagate Barracuda 7200.9, model ST3250824AS
• Modern SSD: Samsung SSD 840 EVO 250GB
• Ramdisk: tmpfs mounted on /tmp

All tests are performed on kernel 3.16.3, 64 bit, on an Intel Pentium G630 (Sandy Bridge, 2 x 2.7GHz).

If you want to replicate the test, just run

sudo tests/benchmark.pl /path/to/test/directory

(the test must be run as root as normal users cannot mount ecryptfs or clear the caches)

• HDD: Seagate Barracuda 7200.9

Test	EncFS	eCryptfs	EncFS advantage
stream_write	32 MiB/s	38 MiB/s	0.84
extract	28744 ms	30027 ms	1.04
du	495 MB	784 MB	1.58
rsync	3319 ms	62486 ms	18.83
delete	6462 ms	74652 ms	11.55

• SSD: Samsung SSD 840 EVO 250GB

Test	EncFS	eCryptfs	EncFS advantage
stream_write	53 MiB/s	75 MiB/s	0.71
extract	26129 ms	9692 ms	0.37
du	495 MB	784 MB	1.58
rsync	2725 ms	8210 ms	3.01
delete	5444 ms	9130 ms	1.68

• Ramdisk: tmpfs

Test	EncFS	eCryptfs	EncFS advantage
stream_write	82 MiB/s	111 MiB/s	0.74
extract	22393 ms	8117 ms	0.36
du	485 MB	773 MB	1.59
rsync	1931 ms	740 ms	0.38
delete	4346 ms	907 ms	0.21

Interpretation

eCryptfs uses a large per-file header (8 KB) which is a big disadvantage on classic HDDs. For stat()-heavy operations on HDDs, EncFS is 18x faster.

EncFS stores small files much more efficiently, which is why it consitently uses less space than eCryptfs: zero-size files take no space at all, other files get a 8-byte header. Because the filesystem allocates space in 4KB blocks, the actually used disk space must be rounded up to 4096.

plaintext size	EncFS raw	EncFS du	eCryptfs raw	eCryptfs du
0	0	0	8192	8192
1	9	4096	12288	12288
1024	1032	4096	12288	12288