Scalability and reliability in a distributed search engine

We have developed a distributed search engine, called cooperative search engine (CSE), in order to retrieve fresh information. In CSE, a local search engine located in each Web server makes an index of local pages. A meta search server integrates these local search engines in order to realize a global search engine. In such a way, the communication delay occurs at retrieval time. So, it is thought to be difficult to search quickly. However we have developed several speedup techniques in order to realize real time retrieval. In addition, the meta server is a single point of failure in CSE. So, we propose redundancy of meta search servers in order to increase availability of CSE. In this paper we describe scalability and reliability of CSE and their evaluations.