Server system and method of performing memory hierarchy control in server system

A memory hierarchy control method performed in a server system that supports an electrical connection memory module and an optical connection memory module, the method comprising:

• determining whether accessed target data is stored in the electrical connection memory module if an access request occurs in the server system;
• reading the target data from the electrical connection memory module when it is determined that the target data is stored in the electrical connection memory module, and determining whether the target data is stored in the optical connection memory module when it is determined that the target data is not stored in the electrical connection memory module;
• and
• reading the target data from the optical connection memory module when it is determined that the target data is stored in the optical connection memory module, and accessing a storage device included in the server system when it is determined that the target data is not stored in the optical connection memory module.

A server system including a channel structure, comprising:

• a first circuit board, which includes a plurality of sockets, the plurality of sockets are connected to a memory controller via an electrical channel;
• a second circuit board, which is combined with the plurality of sockets in signal units of the channel structure, such that signals are exchanged with the memory controller via an electrical channel and an optical channel;
• and
• at least one optical connection memory module is disposed on the second circuit board such that signals are exchanged with the memory controller via the optical channel.