Configure multiple IBM® Content Search Services search servers to distribute the load and allow more full-text indexes to be searched in parallel. Dedicate each server to either Index or Search mode as opposed to the dual IndexAndSearch mode. Multiple search servers are especially helpful if your content-based retrieval (CBR) queries typically search many full-text indexes.
Do not collocate index and search server instances on the same machine. Collocation means that the index and search servers share the same file system cache, which effectively reduces the cache size for the search server. A smaller cache size results in slower query performance because the search server must access the disk more often.