Server system and method of switching server

A server system, comprising:

• a primary server including:
• a first memory;
• and
• a first processor coupled to the first memory;
• and
• at least one synchronous backup server, each including:
• a second memory;
• and
• a second processor coupled to the second memory and the second processor configured to:
• back up data of the primary server in a synchronous manner;
• and
• at least one asynchronous backup server, each including:
• a third memory;
• and
• a third processor coupled to the third memory and the third processor configured to:
• back up data of the primary server in an asynchronous manner,
• wherein the first processor is configured to:
• control each of one or more of the at least one asynchronous backup server to operate as a synchronous backup server when detecting that a number of the at least one synchronous backup server decreases due to a failure in the at least one synchronous backup server included in the server system such that the number of at least one synchronous backup server is adjusted within a predetermined upper limit value.

A method of switching a server, the method comprising:

• detecting a failure in a primary server included in a server system by at least one synchronous backup server or by at least one asynchronous backup server included in the server system and backs up data of the primary server;
• upon detecting the failure in the primary server, promoting the at least one synchronous backup server to operate as a new primary server;
• comparing a synchronization state of the at least one asynchronous backup server with respect to the primary server;
• and
• promoting the at least one asynchronous backup server to operate as a new synchronous backup server such that a number of at least one synchronous backup server is adjusted within a predetermined upper limit value.