post indexer is exelent, but the speed of indexing post is so dull

I will operate a multi-site having 500,000 posts imported from other multi-sites. The defaut tool does not effect. So I search and find a good indexer, Post Indexer. This is good at indexing but gathering post is slow enough to make me crazy.

I found the messages in the dashboard that read
1st pass(25 sites/batch)...
2st pass(5 sties, 5posts/batch)
...

I suppose, if batch time is shorter than 5 min, the speed of indexing is faster than now.

Is it right?

Please let me know of any faster method or where i find and how fix the setting value for speed up.

Many thanks in advance.