Comment 3 for bug 1267494

I don't think the prior upgrade to 3.x is necessary, unless some 3.x-specific features are to be used (like preordered events). New writeset format should not be essential for 5.6 operation. However one more circle will still be needed to get rid of socket.checksum=1 (note that the last node to upgrade to 3.x does not need to set that). So, since we're still going for 2 rounds, it may be worthwhile, to exercise some caution and upgrade one at a time: first Galera and then MySQL version.