Issue: What does the setting of Performance of Maximum, Partially and Reduce in the crawl/indexer stands for in SharePoint MOSS 2007

Solution: Please see below the details of it.

The number of threads the system will use is based on the settings you make to the Indexer Performance setting and will be as follows.  In large scale environments it is recommended that you set this to Maximum, keeping in mind that you can use Crawler Impact Rules to reduce/increase the number of threads per host to reduce the load you are placing on each repository :

• Indexer Performance - Reduced
• Total number of threads: number of processors
• Max Threads/host:  number of processors
• Indexer Performance - Partially reduced
• Total number of threads: 4 times the number of processors
• Max Threads/host: number of processors plus 4
• Indexer Performance - Maximum
• Total number of threads: 16 times the number of processors
• Max Threads/host: number of processors plus 4

There is a hard-coded max on the number of crawl threads of 64.