Storage overhead of duplicacy/how much space is used for metadata/bookkeeping/etc?

When I run duplicacy check, I get:

1 snapshots and 41 revisions
Total chunk size is 8563G in 1831309 chunks

I did a few rounds of pruning and creating new backup revisions just before the latest revision to clean up old chunks. However, Backblaze B2 still reports 9,194.8 GB in use in the bucket. 632 GB of overhead seems like a lot – is this normal?

Is the bucket set to “keep all versions” of the files?

2020-07-22 17.36.13 9085ae666a9d

Another point is that it takes some time for file exclusions to be reflected in the total reported size.

Yes, I recently set it to keep all versions because of a scary-sounding issue (another thread on this forum) with missing chunks. However before I set that, the overhead % was about the same. It’s also my understanding that when prune deletes, it really deletes so all the versions go away, and this is corroborated by the fact that my last prune removed about 500 GB from my B2-reported storage.

I checked one of my buckets:

3 snapshots and 278 revisions
Total chunk size is 27,515M in 27411 chunks

B2 reports:

2020-07-22 20.03.06 4e151daacc37

And Cyberduck:


So, maybe it is related to GB x GiB.

difference = 7,3%

1 Gibibyte = 1,07374 Gigabyte => 7,374 %

Ahhh, astute observation, thank you! Yes, that explains it. Just to try it out, I did a straight upload of a file with 2^30 = 1073741824 bytes to a fresh B2 bucket, and it indeed shows “Current Size: 1.1 GB”

Thanks Backblaze for telling us that you always use the base-2 version. Ugh.

How Many Bytes Are in a Megabyte? Really? - “whenever you see a measurement presented, it is always based on 1024x”
Why do my backed up files appear smaller on Backblaze than on my Mac? – Backblaze Help

Keywords for future travellers: Backblaze B2 uses the base-10/1000-based kilobyte, megabyte, gigabyte and not the base-2/1024-based kibibyte, mebibyte, gibibyte when displaying B2 bucket sizes.

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