Nexus version 2 to 3 upgrade - File System Hard Linking


We have been working on to upgrade nexus version 2 of our existing env to nexus 3 version using ‘File System Hard Linking’ method which is mentioned as fastest ways to migrate.

However our nexus 2 repository consists of 11TB of data in the repositories hence the upgrade process is taking more than 3-4 days and keep running still. Any ways to handle the size of higher volumes in migration ?
Since this is taking multiple days to complete the migration, it’s a challenge to keep our live nexus 2 env in on-hold for days. Any other alternative ways when a repository consists of that much of volume to handle?