This is from late December 2011:
Shay: "Note, if you want to run several instances on the same box, a
feature needs to be added to make sure that a shard and a replica
won't be allocated on the same machine (not node), which is quite
simple to add, can you open a feature? "
I looked and searched through ES issues on Github and couldn't find
one that matches the above, which would mean ES could still place the
replicate on the same machine as its original shard.
Shay, if the above is still the case (is it?), I'll open an issue.