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Problem: Utilise 7-zip to package objects but without compression (Copy mode) #46

ross-spencer opened this issue Jul 30, 2018 · 2 comments


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commented Jul 30, 2018

Please describe the problem you'd like to be solved.

7z offers a storage level wrapper called 'copy' that means the package that is created for a zip file will not use compression. AIPs can be wrapped without using compression which might be less-risky to future preservation and access.

Describe the solution you'd like to see implemented.

Provide a new chain link choice that allows for the selection of 'copy' or no-compression from the processing configuration.

Additional context

Docs on compression options available to 7z:

@ross-spencer ross-spencer self-assigned this Jul 30, 2018

@ross-spencer ross-spencer added the IISH label Jul 30, 2018

@ross-spencer ross-spencer added this to the 1.8.0 milestone Jul 30, 2018


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commented Jul 31, 2018

To test:

Complete an ingest with the compression option: 7z without compression (Copy)

Look at the pointer file and observe the command options:

program=7z; algorithm=copy; version=p7zip Version 9.20 (locale=en_US.UTF-8,Utf16=on,HugeFiles=on,4 CPUs)

The outputs may vary, but observe the algorithm should be Copy

Finally, download the AIP and using the following 7z command: $ 7z t <aip-name>-d98c6ff1-931c-4523-96aa-600acc593a0b.7z, look for the method which should also equal Copy.

7-Zip [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21
p7zip Version 16.02 (locale=en_NZ.UTF-8,Utf16=on,HugeFiles=on,64 bits,4 CPUs AMD A6-5200 APU with Radeon(TM) HD Graphics     (700F01),ASM,AES-NI)

Scanning the drive for archives:
1 file, 97157 bytes (95 KiB)

Testing archive: 5-d98c6ff1-931c-4523-96aa-600acc593a0b.7z
Path = 5-d98c6ff1-931c-4523-96aa-600acc593a0b.7z
Type = 7z
Physical Size = 97157
Headers Size = 629
Method = Copy
Solid = -
Blocks = 13

Everything is Ok

Folders: 12
Files: 13
Size:       96528
Compressed: 97157

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commented Sep 28, 2018

In my test, the Processing Configuration setting "Select compression algorithm" was set to "7z without compression (Copy)" and an AIP was created from Demo files.
As per the instructions above, the algorithm value in the pointer file was "copy".
After downloading the AIP the 7zip t command resulted in a successful output "Method = Copy Delta" (see below).
screen shot 2018-09-28 at 11 14 50

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