takes an hour

[Brian Whitman]

I have a largish solr store (2.4m documents with lots of stored text,  
27GB data dir) and I ran optimize on it last night. The QTime was  
3605096 !  (The commit took about a minute.) During the optimize the  
solr java process had 50% CPU and was using all of its max heap size.  
(1GB) On a server that's doing other stuff it was a bit much.

What is optimize doing (from a user's standpoint), how often should I  
run it, is it necessary?

Can I do the optimize on an rsync'd (non-live) copy of the index and  
then sync it back?