Patent ID: 7100070
Filing Date: 2006-08-29
Classification: H04L

Abstract:
1. A computer system comprising: a primary site that comprises a primary server for providing a client with a service and a primary storage connected to the primary server and storing data to be provided to the primary server; a secondary site that comprises a secondary server for providing the client with the service and a secondary storage connected to the secondary server and storing data provided to the secondary server, the secondary site operating when a failure takes place in the primary server, which is for regular operation, the primary storage and the secondary storage comprising a remote copy unit to make contents stored in the primary storage and contents stored in the secondary storage identical to each other; and a DNS server for providing DNS information, which gives the client an access to the server that provides the service, wherein the DNS information obtained from the DNS server is recorded by the client along with information that defines a time to live of the DNS information, wherein the primary server comprises a primary request log processing unit, a primary site processing unit, and an application unit, wherein the application unit receives a data input/output request from the client and sends a result of processing made upon the request to the client, wherein the primary site processing unit detects whether it is possible to communicate with the secondary site or not, wherein, when the primary site processing unit detects that communication with the secondary site is impossible, the primary request log processing unit sends identification number to be attached to the data input/output request along with the result of the processing made upon the data input/output request, instructs to record, in a request log, with the identification number, the request sent from the client to the primary server, and instructs to shorten the recorded time to live of the DNS information, wherein the secondary server comprises a secondary request log processing unit, a secondary site processing unit, and an application unit, wherein the secondary site processing unit detects whether it is possible to communicate with the primary site or not, and wherein, when the secondary site processing unit detects that communication with the primary site is impossible, the secondary request log processing unit increases a frequency of monitoring the primary site, takes a snapshot of the primary storage, starts preparation of providing the service to the client on the secondary site using the taked snapshot, and instructs to shorten the recorded time to live of the DNS information.