Lets also clearup the doc for this stuff as part of the issue....
yes the wiki has to be cleaned up too
Are backups made in the same format as the scripts method
The format is same (same dir name format). The mechanism is different. scripts use hard links , this uses copying
Is it possible to replicate a backup or just the live index?
nope. only live index can be transferred. The backup can be made the live index and then the user can replicate it. There is a file called index.properties in the dataDir (only created by replicationhandler. but users can create them too ). It can take a property index=<dir-name> which tells solr core where to load the index from. users can edit that and do a reload core for the new backup to be used as the index.
what happens when you shutdown during a replication - does Solr wait? Abort? If its aborts, are the temp files cleaned up later?
replication is aborted. temp files will remain as is. They will not be cleaned up automatically. But presence of those temp files will not have any impact of future replication.
replicate and polling both to default to on right?
and the replicate setting just stops any slaves hitting a master with replicate=off from syncing?
the slaves will keep polling even if the master has disabled replication . But the master will respond with "no changes" .This will ensure that when the replication is re-enabled from master , the slaves will be able to resume replication