On Fri, Oct 4, 2013 at 9:09 AM, Paulo Motta <pauloricardomg@gmail.com> wrote:
I manually tried to insert and retrieve some data into both the newly upgraded nodes and the old nodes, and the behavior was very unstable: sometimes it worked, sometimes it didn't (TimedOutException), so I don't think it was a network problem.

The number of read timeouts diminished as the number of upgraded nodes increased, until it reached stability. The logs were showing the following messages periodically:

... 

Both of these issues relate to upgrading from 1._0_.x to 1.2.x, which is not supported.

Were I you, I would summarize the above experience in a JIRA ticket, as 1.1.x to 1.2.x should be a supported operation and should not unexpectedly result in decreased availability during the upgrade.

=Rob