A method for warming up index files while continuing providing a search service, wherein the search service is provided by at least one search node in a search system, a first index file is stored in a disk in the search node and a first group of pages from the first index file is stored in a cache in the search node, the method comprising: storing a second index file into the disk in the search node; receiving a plurality of queries during the search service; determining a plurality of warm-up queries from the plurality of queries, wherein the plurality of warm-up queries is used in warm-up searches, wherein the determining the plurality of warm-up queries comprises: selecting the plurality of warm-up queries from the plurality of queries based on a gradually increasing query replication rate, wherein the query replication rate indicates the ratio of the number of plurality of warm-up queries to the number of the plurality of queries; in response to selecting each query, performing a warm-up search based on the second index file, wherein the warm-up search is performed concurrently to the search node still continuing providing the search service based on the first index file and without the need of interrupting the search service; and storing a second group of pages in the second index file into the cache based on the results of the warm-up search; wherein the search service is provided based on the second index file after the warming up is completed. storing a second index file into the disk in the search node; receiving a plurality of queries during the search service; determining a plurality of warm-up queries from the plurality of queries, wherein the plurality of warm-up queries is used in warm-up searches, wherein the determining the plurality of warm-up queries comprises: selecting the plurality of warm-up queries from the plurality of queries based on a gradually increasing query replication rate, wherein the query replication rate indicates the ratio of the number of plurality of warm-up queries to the number of the plurality of queries; in response to selecting each query, performing a warm-up search based on the second index file, wherein the warm-up search is performed concurrently to the search node still continuing providing the search service based on the first index file and without the need of interrupting the search service; and storing a second group of pages in the second index file into the cache based on the results of the warm-up search; wherein the search service is provided based on the second index file after the warming up is completed. selecting the plurality of warm-up queries from the plurality of queries based on a gradually increasing query replication rate, wherein the query replication rate indicates the ratio of the number of plurality of warm-up queries to the number of the plurality of queries; in response to selecting each query, performing a warm-up search based on the second index file, wherein the warm-up search is performed concurrently to the search node still continuing providing the search service based on the first index file and without the need of interrupting the search service; and storing a second group of pages in the second index file into the cache based on the results of the warm-up search;