12

Rsync has command line arguments for compression:

-z, --compress              compress file data during the transfer
    --compress-level=NUM    explicitly set compression level

What does --compress-level mean? Which numbers can be used as level?

14

it's values between 0-9. Where 1 is fastest 9 is most compressed. Other than that there's correlation between rsync and zlib where about rsync tells the zlib library to "use the default compression", in zlib's docs, it says this:

Z_DEFAULT_COMPRESSION requests a default compromise between speed and compression (currently equivalent to level 6).

  • So, the origin of these levels is zlib? – cronfy Nov 18 '16 at 8:52
  • yes, but you will be able if you set value for example in rsync 0 then it would uncompressed and then send in that form. – Michal Nov 18 '16 at 8:53
0

The environment used was composed by two docker containers used with MACVLAN + some noise traffic (which gives around ±1% error) The fileX - in my case - is a binary one

So, below are the result of rsync tarred files versus rsync with compression (option -z) untarred files

      1. File tarred + rsync without compression (rsync -axvPAH fileX.tar destination:/path)

    File size is 56933 bits (fileX.tar)
    Transfer difference is 4735665-4673346=62319 bits

      2. File tarred + rsync with default compression (rsync -axvPAH -z fileX destination:/path)

    File size is 56933 (fileX.tar)
    Transfer difference is 4933845-4871608=62237

      3. File tarred + rsync with maximum compression (rsync -axvPAH -z --compress-level=9 fileX.tar destination:/path)

    File size is 56933 bits (fileX.tar)
    Transfer difference is 4870664-4808387=62277

      4. File untarred + rsync with default compression (rsync -axvPAH -z fileX destination:/path)

    File size is 237525 bits (fileX)
    Transfer difference is 4669946-4607637=62309 bits

      5. File untarred + rsync with maximum compression (rsync -axvPAH -z --compress-level=9 fileX destination:/path)

    File size is 237525 bits (fileX)
    Transfer difference is 4806735-4744764=61971 bits

      6. File untarred + rsync without compression (makes no sense since it’s the most bandwidth consuming one) 

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