I don't know the specific answer to your question but I do have a data point to add. When I was just starting out in my career in the early 2000s, I worked for

I don't know the specific answer to your question but I do have a data point to add. When I was just starting out in my career in the early 2000s, I worked for a hedge fund. One curious thing I noticed is that all the traders had time stamping machines on their desks that are inspected and sealed regularly. I was told that during an outage, these timestamp machines allow trades to continue to happen because the trader can write down the order and stamp it and their counter party would presumably do the same. Later the orders can then be reconciled when things are back up and running. This leads me to think that it is at the very least possible for transactions to be recorded in a distributed manner. Example of machine: http://www.carpenterstimesystems.com/Amano-TS3000i-OATS-Time-Validation-Clock-System.html http://www.carpenterstimesystems.com/Amano-TS3000i-OATS-Time... This might all be historical now.