a server coupled to another server via a network; and

a storage system coupled to said server;

wherein said server comprises a buffer memory and a processor,

wherein said storage system comprises:

a plurality of disk devices;

a journal log storage area; and

a disk controller coupled to said disk devices;

wherein said processor included in said server:

receives an update request from said another server;

updates data on said buffer memory; and

sends a journal log to said storage system, said journal log being an update history information of updated data on said buffer memory and including both said updated data and a block address used to specify areas of one or more of said plurality of disk devices;

wherein said disk controller included in said storage system:

receives said journal log from said server;

stores said journal log into said journal log storage area;

wherein said processor sends a flush request to said storage system;

wherein in response to said flush request, said disk controller:

reads said journal log from said journal storage area;

sends a flush processing completion notification to said server; and

stores, into said one or more of said plurality of disk devices, said updated data included in said journal log using said block address; and

wherein said processor manages said update data on said buffer memory as dirty data until receiving said flush processing completion notification from said storage system such that said processor, before receiving said flush processing completion notification from said disk controller, executes a process using said updated data on said buffer in response to receiving an access request from said another server.