The basic problem is that the page content dumps are ordered by revision number within each page, which makes good sense for dumps users but means that the addition of a single revision to a page will shift all of the remaining data ,resulting in different compressed blocks. That's going to be true regardless of the compression type.

In the not too distant future we might switch over to multi-stream output files for all page content, fixing the page id range per stream for bz2 files. This might let a user check the current list of page ids against the previous one and only get the streams with the pages they want, in the brave new Hadoop-backed object store of my dreams. 7z files are another matter altogether and I don't see how we can do better there without rethinking them altogether.

Can you describe which dump files you are keeping and why having them in sequence is useful? Maybe we can find a workaround that will let you get what you need without keeping a bunch of older files.

Ariel

On Tue, Jul 28, 2020 at 8:48 AM Count Count <countvoncount123456@gmail.com> wrote:
Hi!

The underlying filesystem (ZFS) uses block-level deduplication, so unique chunks of 128KiB (default value) are only stored once. The 128KB chunks making up dumps are mostly unique since there is no alignment so deduplication will not help as far as I can see.

Best regards,

Count Count

On Tue, Jul 28, 2020 at 3:51 AM griffin tucker <gtucker4.une@hotmail.com> wrote:

I’ve tried using freenas/truenas with a data deduplication volume to store multiple sequential dumps, however it doesn’t seem to save much space at all – I was hoping someone could point me in the right direction so that I can download multiple dumps and not have it take up so much room (uncompressed).

 

Has anyone tried anything similar and had success with data deduplication?

 

Is there a guide?

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