I’m running TrueNAS Scale 24.10 and have a dataset shared via SMB using the Basic Time Machine Share preset. I back up my Mac to this share once a week, and it typically uploads around 10 GB of new data.
After each backup, I have a Cloud Sync task to sync the dataset to a Backblaze B2 bucket. However, during the dry run, it reports over 150 GB of changed data to upload—even though only ~10 GB was added by Time Machine. It does this every week.
This is a problem because I have a 1 TB monthly upload data cap, and these unnecessary uploads are eating into it fast.
Has anyone dealt with this issue? Is there a way to reduce the amount of data that gets uploaded to B2 while still using Time Machine?
Time Machine is a disk image split into bands. When you create a new backup new data is written and it may result in multiple bands added and/or modified. Then when you sync each band needs to be uploaded in its entirety, even if only a few bytes changed. If your Time Machine is encrypted — the data spread is even more amplified.
The advice is to not sync Time Machine to Backblaze. Time Machine is a local backup. It contains a lot of data that is nice to have if bandwidth and storage is not a concern but can be 100% omitted from offsite backup. Stuff like derivative data in your photos library and browser databases.
Instead, use another tool to backup your actual source data (without derivative; using photos library again as an example — pick only originals folder) to Backblaze. There are many options to choose from. On a Mac Arq7 is a solid choice. It will also take care of dataless files, which are missing from Time Machine but still need to be backed up.
