When I started Adding Blu-ray content, my process was:

1. use my late 2008 MacBook Pro to convert the Blu-ray to an MKV file
   
2. transfer the MKV over to my 2012 Mac mini, because it was 3x faster than the MBP
   
3. convert the MKV to an M4V file (H.264) via Handbrake
   

After that, I left the MKV files on the Drobo. In part because I had the space, and in part because I foresee that in the near future I'll be converting the content into H.265 as iOS devices are starting to support the more efficient format.

Last night realized that the MKV files where using up 2 TB of storage on the Drobo. When I added the second 6TB drive, I pulled out a 3TB drive and put it in an enclosure for my Mac Pro. It's mostly empty, so I temporarily connected the enclosure to the Mac mini and moved all the MKV files to the 3TB drive.

Now the Drobo has plenty of room:

The other benefit is my new Mac Pro is faster than the mini, so having the MKV files already on the Mac Pro will be beneficial when it's time to convert to H.265.