When should I use multiple instances of SOLR?

I need to index three completely unrelated elements (say, products, blog posts, location).

No where there will be a search that will combine results from this elements.

Intuitively, it makes sense to me to separate and index each element in it's own instance of SOLR. I guess I can use one instance and then have some extra field to differentiate each element, so they won't return in the same query.

Which approach is the best? (three elements, totally un-related, 10 of thousands of reco开发者_Python百科rds each).

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If you have 3 completely unrelated elements, its better to maintain different cores for each of the elements.
There still would be a single instance of Solr, however you would be using separate cores for each of your elements.
This will help you to maintain, configure, build the different elements independantly

More info @ http://wiki.apache.org/solr/CoreAdmin