You didn’t mention how big those volumes are and how frequently the data changes.

Assuming it’s not that much data:

• use tar to archive each volume first, while using proper options to preserve permissions and whatever else is important for your usecase
• use restic to backup those archives
• use a proper pruning strategy to not let your backups get too big:
  • I’m not that familiar with restic, but maybe you can backup those archives separately and apply a more aggressive pruning strategy just for them
  • simply might be needed, cause deduplication (AFAIK) might not be that great with backing up archives
  • but maybe if the volume data and the resulting archive doesn’t change that often, deduplication would be sufficient even with a not so aggressive pruning strategy