Solr Search Index Backups?

If you have a massive set of documents that you’re using Solr to search (let’s say a few million HTML pages) how much should you worry about losing the search index?

It is of course always possible to reindex the original documents, but that would take a fair while, so should you keep a backup of the search index? If you restored the backup, how would you identify which documents needed updating?

Solr seems to support replication – should you just use that as a constant backup that you can swap over to using if something goes wrong?

So many questions…

And it looks like there are answers out there somewhere – Solr has a bunch of tools related to backups and stuff. Looks promising, though the documentation doesn’t really say what the best practices are at least there are tools that look like they help you manage the search indexes.