Is it safe to backup concurrently to one S3 repo?

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1

I’m using the same S3 bucket (to benefit from dedup) from two computers, but I’m wondering if this is safe.

What happens if two backups are started at the same time? Is there some locking involved to make sure only one can proceed, or alternatively perhaps is this already completely safe without locking?

I’m using Ceph S3 as the S3 backend. I noticed that it has the per-bucket option to enable locking but I don’t have it enabled. On the other hand I did not find the word ‘lock’ from the S3 code of Kopia, so I’m not sure if it would even use it if it were available (I don’t know how locking would be used, though).

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Yes, it is safe. Kopia does not use locking and in the worst case (when new content is backed up simultatenously from 2 machines) you will not get deduplication, which will be fixed over time when maintenance gets a chance to compact the repo.

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