Paxos vs. Blockchain: A User's Perspective

A robust distributed system can tolerate partial failures in the system - that means that the system should continue to work as expected even if parts of it are failing.  There are 3 main 'partial failures' that the field of Distributed Systems tries to solve for:

1.) Out-of-sync system clocks
2.) Process pauses
3.) RPC requests with no response

Paxos is one algorithm that tries to solve for these by using consensus among nodes to decide on the sequence and order of events, but system administrators must tune the timeout parameter to find the best middle ground between waiting too long for a node (one computer in the network of systems) and not waiting long enough.

The blockchain algorithm gets around the idea of time entirely by deciding on an order of events once, and then getting as many nodes as possible to agree and persist the actual ordering itself.  Here's an excerpt straight from Satoshi's paper itself:

The solution we propose begins with a timestamp server. A timestamp server works by taking a hash of a block of items to be timestamped and widely publishing the hash, such as in a newspaper or Usenet post. The timestamp proves that the data must have existed at the time, obviously, in order to get into the hash. Each timestamp includes the previous timestamp in its hash, forming a chain, with each additional timestamp reinforcing the ones before it.

For those interested in advanced Distributed Systems concepts, learning about blockchain is a great way to expand your knowledge and play with the latest ideas in consensus.

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