Upgrading from 1.3.1 -> latest version (2.1.0)


We have a cluster with 2 masters (that also store data) and 1 master "coordinator" that does not store data.

We recently restarted one of our masters that stores data and were hit with the bug outlined here: https://www.elastic.co/blog/elasticsearch-1-3-2-released

we were able to apply the fix mentioned, but nonetheless would like to upgrade to the latest version. It seems the latest version is 2.1.0

My question is, would we be able to take down one master at a time, install the new version and bring it back up. that way there would be no downtime? When we bring up the newly updated node, will it be able to work well with the nodes that are currently still on 1.3.1?

1.x -> 2.x requires a full cluster restart. Here are the rules.