Include other compressors like XZ for smaller size and LZO for speed

[vescudero]

Although Attic make a good job deduplicating data, it seems it uses a simle deflate method for compression (like the ones of zip and gzip).

However for data that is going to be backup once for the long term, it makes sense to take a different approach. XZ (Parallel lzma as in zbackup) is in my opinion one of the best compression you can get to further reduce the size at the expense of more cpu and extra time to encrypt and only a little bit more work to restore. For low-end computers or quick short term backups, LZO is the way to go, it's much much faster during compression and decompression at the expense of smaller compression rate.

[skarekrow]

I agree, I think XZ is a great compression format and I +1 this.
On 9/16/2014 3:33 PM, Victor Escudero wrote:

Although Attic make a good job deduplicating data, it seems it uses a
simle deflate method for compression (like the ones of zip and gzip).

However for data that is going to be backup once for the long term, it
makes sense to take a different approach. XZ (lzma) is in my opinion
one of the best compression you can get to further reduce the size at
the expense of more cpu and extra time to encrypt and only a little
bit more work to restore. For low-end computers or quick short term
backups, LZO is the way to go, it's much much faster during
compression and decompression at the expense of smaller compression rate.

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#114.

[imraro]

I vote for lz4!

[vks]

Note that LZMA is part of Python since version 3.3.

[vks]

Replacing zlib with lzma yields the following failures:

======================================================================
ERROR: test_keyfile2 (attic.testsuite.key.KeyTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "attic/build/lib.macosx-10.9-x86_64-3.4/attic/testsuite/key.py", line 77, in test_keyfile2
    self.assert_equal(key.decrypt(self.keyfile2_id, self.keyfile2_cdata), b'payload')
  File "attic/build/lib.macosx-10.9-x86_64-3.4/attic/key.py", line 128, in decrypt
    data = decompress(self.dec_cipher.decrypt(data[41:]))  # should use memoryview
  File "attic/build/lib.macosx-10.9-x86_64-3.4/attic/key.py", line 19, in decompress
    return lzma.decompress(data)
  File "/usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/lib/python3.4/lzma.py", line 498, in decompress
    res = decomp.decompress(data)
_lzma.LZMAError: Input format not supported by decoder

======================================================================
FAIL: test_keyfile (attic.testsuite.key.KeyTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "attic/build/lib.macosx-10.9-x86_64-3.4/attic/testsuite/key.py", line 62, in test_keyfile
    self.assert_equal(key.extract_nonce(manifest2), 1)
AssertionError: 4 != 1

======================================================================
FAIL: test_passphrase (attic.testsuite.key.KeyTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "attic/build/lib.macosx-10.9-x86_64-3.4/attic/testsuite/key.py", line 92, in test_passphrase
    self.assert_equal(key.extract_nonce(manifest2), 1)
AssertionError: 4 != 1

----------------------------------------------------------------------
Ran 112 tests in 35.280s

FAILED (failures=2, errors=1, skipped=8)

[ThomasWaldmann]

I am currently working on implementing support for other compressors than zlib.

Current status:

• flexibility: done
• lzma: done
• null: done

See PR #207. After this is merged, adding new compression algorithms gets very easy as the infrastructure is already in place.