Hi.
today I did master switch for
en.wikipedia.org to mysql5.1, we have been running s2
(twenty other major languages) for few days on fully-5.1 setup.
Some higher level description of the branch is at
http://wikitech.wikimedia.org/view/MySQL_5.1_(fork)
Actual tree is at
https://code.launchpad.net/~wikimedia/sakila-server/mysql-5.1-wm
Actual upgrade happened with no downtime, and there're no horror stories to tell about
the process, was way too smooth.
Rest of cluster wil follow soon.
Cheers,
Domas