I'll try to answer to the questions
@JamesG the 32 chars are the key , you need to keep this key, if not you won't be able to restore anything. IF the key is wrong you'll have an error message when connecting to the remote.
I am glad to see that S3 is now stable enough for you all. To improve it again, we are planing to implement retry every times it is possible. It is already implemented during the reading of the backup in NBD, please give it a try.
There is also a test branch ( https://github.com/vatesfr/xen-orchestra/pull/6840 ) that should improve concurrency handling when using NBD reading and writing to S3
For now, you should test it on a separate job with a big VM
The merge is mostly a copy and delete of all the block (1-2MB each) that are not used anymore. This step could probably by speed up further, but we prioritized reliability here, since it can break the full backup chain it something go wrong ( and thanks @andrew for your time on this feature). You can set
mergeBlockConcurrency to a higher value ( like 8 ) in the backups section of your config file
You can also increase writeBlockConcurrency in the backup section of the config file to speed up transfer, especially when coupled with the test branch
The easiest way to ensure your config file is not reset on each update is to create the config in ~/.config/xo-server/config.toml (use the home directory of the user running XO )
If you have a xoa, use /etc/xo-server/config.toml
[backups] writeConcurrency = 32 mergeConcurrency = 8