Fast Photos Library backup to external share over ThunderBolt

I've been running some benchmarks for backing up a large (45 GB) Photos Library (stored on an external SSD) from an M2 Mac mini (2023) to an Intel Mac mini (2018) (to an external SSD). The 2 machines are linked via a short ThunderBolt cable (TB4 port on the M2, TB3 port on the Intel). Transfer speed will depend on many factors but here is a summary of what works best in my setup:

1. Convert the Photos Library to AAR format using the Archive Utility. This converts the Photo Library package to a single file for efficient transfer. The Archive Utility runs very efficiently on Apple Silicon.
2. Using Finder on the Mac mini (2018), copy the AAR file from the disk share to the local external SSD.
3. [optional] Double click on the transferred AAR file to restore the backup to a Photos Library format on the Mac mini (2018)

Step 1 & 2 take about 5 minutes to copy the archive. Step3 takes an additional 5 minutes on the Mac mini (2018) but is only necessary to recover the Photos Library in its original format.

Setting up the external disk share to only use ThunderBolt can be a bit tricky. My recommendation is to temporarily set any other network interfaces to Inactive (on both machines) before mounting the disk share. This method allows you to mount a volume by name but still guarantee that the ThunderBolt interface will be used exclusively.

In passing, I tried but was unsuccessful setting up multichannel SMB over ThunderBolt (i.e. using 2 ports on each machine for faster transfers).

Any feedback or additional recommendations would be much appreciated.

- Pie Lover