Failing local backup drive missing chunks, restore from backup copy?

[aldinach]

Hello - one of my backup drives (which is mirrored to the cloud) is failing and has a number of missing chunks. I plan to replace the drive and copy over what data I can to the replacement, but I’ll still end up with a bunch of missing chunks due to corruption of the backup disk.

Is there an (easy) way to just restore the missing chunks from the cloud storage to my local storage once I replace the disk? It’s an 8TB disk so I’d rather not have to download the entire set of files from the cloud if I can avoid it.

If this will prove to be quite complex, the backups on this disk are from relatively static data, so I can just recreate the job as an alternative plan, but I thought I’d try to download the missing chunks first.

Thanks for the help!

PS: I did find this similar topic but am not sure if the advice here holds true for me as well since I only want to fill in the missing chunks locally as opposed to downloading the entire disk’s contents.

[Droolio]

Out of curiosity, how is your backup drive ‘mirrored to the cloud’? Via Dupliacy copy, Rclone/rsync, or some other means?

Either way, if both storages were initialised to be copy-compatible with one another, one way to do this would be to rename the /snapshots directory to say, snapshots.bak, on your local side, and then Duplicacy copy the storage from cloud. Only missing chunks are downloaded.

After, you can decide whether or not to keep the original /snapshots directory, or the new one created from your recent cloud copy. For example, you could put it back, and copy again in either or both directions to maintain the fullest snapshot history.

Make sure to run a thorough check -chunks and maybe delete the cache for that if you ran it before.

Tidy up with prune -exhaustive.

[aldinach]

Thank you for the answer @Droolio . The mirror to backblaze is done daily using the Duplicacy copy command and they were initialized to be compatible in the beginning. I really appreciate your suggestion and will give the copy from the cloud to local a try once the drive has been restored. Thank you!

[aldinach]

Just a quick report back that this worked flawlessly. I only had to download 9GB from Backblaze to repair the corrupted bits (of an 8TB drive) locally, and everything is back to working as it was. I was anticipating having to spend MUCH more time getting things back in working order. Huge compliments to the maintainers/creators of Duplicacy as the offsite backup copy worked exactly as it should to recover from a local failure.