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104 lines
3.9 KiB
Markdown
104 lines
3.9 KiB
Markdown
EncFS Performance
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=================
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EncFS runs in user-space while eCryptfs runs in the kernel.
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This is why it is often assumed that eCryptfs is faster than EncFS.
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To compare the actual performance of EncFS and eCryptfs on top of
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different backing disks, the EncFS test suite contains an automated
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performance test - [benchmark.pl](tests/benchmark.pl).
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performance.pl takes care of setting up EncFS and eCryptfs mounts,
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clearing caches and syncing disks between the tests, and also to unmount
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and clean up everything in the end.
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It performance the following tests:
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* stream_write: Write 100MB of zeros in 4KB blocks
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* extract: Extract the [linux-3.0.tar.gz archive](https://www.kernel.org/pub/linux/kernel/v3.x/)
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* du: Disk space used after extraction, in megabytes
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* rsync: Do an "rsync -an" of the extracted files.
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This simulates an rsync to a destination that is
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(almost) up-to-date. The workload consists mostly
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of stat() calls.
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* delete: Recursively delete the extracted files
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For EncFS, the [default options](tests/benchmark.pl#L47) are used.
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This means:
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* AES with 192 bit key
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* Filename encryption
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For eCryptfs, the [options used](tests/mount-ecryptfs.expect) are
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* AES with 128 bit key
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* Filename encryption
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For all the details, take a look at [benchmark.pl](tests/benchmark.pl) .
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Results
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-------
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The performance of an overlay filesystem depends a lot on the performance
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of the backing disk. This is why I have tested three different kinds of
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disk:
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* Classic HDD: Seagate Barracuda 7200.9, model ST3250824AS
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* Modern SSD: Samsung SSD 840 EVO 250GB
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* Ramdisk: tmpfs mounted on /tmp
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All tests are performed on kernel 3.16.3, 64 bit, on an Intel Pentium
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G630 (Sandy Bridge, 2 x 2.7GHz).
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If you want to replicate the test, just run
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sudo tests/benchmark.pl /path/to/test/directory
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(the test must be run as root as normal users cannot mount ecryptfs or
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clear the caches)
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* HDD: Seagate Barracuda 7200.9
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Test | EncFS | eCryptfs | EncFS advantage
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----------------|-------------:|-------------:|---------------:
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stream_write | 32 MiB/s | 38 MiB/s | 0.84
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extract | 28744 ms | 30027 ms | 1.04
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du | 495 MB | 784 MB | 1.58
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rsync | 3319 ms | 62486 ms | 18.83
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delete | 6462 ms | 74652 ms | 11.55
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* SSD: Samsung SSD 840 EVO 250GB
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Test | EncFS | eCryptfs | EncFS advantage
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----------------|-------------:|-------------:|---------------:
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stream_write | 53 MiB/s | 75 MiB/s | 0.71
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extract | 26129 ms | 9692 ms | 0.37
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du | 495 MB | 784 MB | 1.58
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rsync | 2725 ms | 8210 ms | 3.01
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delete | 5444 ms | 9130 ms | 1.68
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* Ramdisk: tmpfs
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Test | EncFS | eCryptfs | EncFS advantage
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----------------|-------------:|-------------:|---------------:
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stream_write | 82 MiB/s | 111 MiB/s | 0.74
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extract | 22393 ms | 8117 ms | 0.36
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du | 485 MB | 773 MB | 1.59
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rsync | 1931 ms | 740 ms | 0.38
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delete | 4346 ms | 907 ms | 0.21
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Interpretation
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--------------
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eCryptfs uses a large per-file header (8 KB) which is a big disadvantage
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on classic HDDs. For stat()-heavy operations on HDDs, EncFS is 18x faster.
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EncFS stores small files much more efficiently, which is why it consitently
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uses less space than eCryptfs: zero-size files take no space at all,
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other files get a 8-byte header. Because the filesystem allocates space
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in 4KB blocks, the actually used disk space must be rounded up to 4096.
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plaintext size | EncFS raw | EncFS du | eCryptfs raw | eCryptfs du
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--------------:|----------:|---------:|-------------:|------------:
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0 | 0 | 0 | 8192 | 8192
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1 | 9 | 4096 | 12288 | 12288
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1024 | 1032 | 4096 | 12288 | 12288
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