NOTE: it's quite likely you don't need to know any of this. but since
you're here...
NOTE: there is currently no way to change a class's replication policy,
except modifying the database, like so:
ALTER TABLE class
SET replpolicy='Union(MultipleHosts(3), OnDevice(13))'
WHERE dmid=3 AND classid=1;
Yes, we know this is sub-optimal. A mogadm command should be
done in the future.
About replication policies strings:
-- if you don't have a colon in a policy, "MogileFS::ReplicationPolicy::"
is prepended to the class name
-- if a class doesn't have a replpolicy value, the historical default
is used: "MultipleHosts()". see MogileFS::ReplicationPolicy::MultipleHosts
for what that does.
-- a replication policy of "MultipleHosts()" uses the class's "mindevcount"
column. but an explicit value, like "MultipleHosts(3)" will ignore the
configured "mindevcount"