Addendum:

To complete the list. Here the parallel implementation of "lzip":

    "plzip": https://www.nongnu.org/lzip/plzip.html

-Ramon

On 26/09/2021 14:23, Ramon Fischer wrote:
> In addition to this, you may want to use the parallel implementations 
> of "gzip", "xz", "bzip2" or the new "zstd" (zstandard), which are 
> "pigz"[1], "pixz"[2], "pbzip2"[3], or "zstmt" (within package 
> "app-arch/zstd")[4] in order to increase performance:
>
>    $ cd <path_to_mounted_backup_partition>
>    $ for tar_archive in *.tar; do pixz "${tar_archive}"; done
>
> -Ramon
>
> [1]
> * https://www.zlib.net/pigz/
>
> [2]
> * https://github.com/vasi/pixz
>
> [3]
> * https://launchpad.net/pbzip2
> * http://compression.ca/pbzip2/
>
> [4]
> * https://facebook.github.io/zstd/
>
>
> On 26/09/2021 13:36, Simon Thelen wrote:
>> [2021-09-26 11:57] Peter Humphrey <peter@prh.myzen.co.uk>
>>> part       text/plain 382
>>> Hello list,
>> Hi,
>>
>>> I have an external USB-3 drive with various system backups. There 
>>> are 350 .tar
>>> files (not .tar.gz etc.), amounting to 2.5TB. I was sure I wouldn't 
>>> need to
>>> compress them, so I didn't, but now I think I'm going to have to. Is 
>>> there a
>>> reasonably efficient way to do this? I have 500GB spare space on 
>>> /dev/sda, and
>>> the machine runs constantly.
>> Pick your favorite of gzip, bzip2, xz or lzip (I recommend lzip) and
>> then:
>> mount USB-3 /mnt; cd /mnt; lzip *
>>
>> The archiver you chose will compress the file and add the appropriate
>> extension all on its own and tar will use that (and the file magic) to
>> find the appropriate decompresser when you want to extract files later
>> (you can use `tar tf' to test if you want).
>>
>> -- 
>> Simon Thelen
>>
>

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