A computer system for switching an operation mode to a Redundant Array of Independent Disks, RAID, operation mode, the computer system comprising: a plurality of hard disk drives, at least one of the hard disk drives containing and executing a boot program normally; a chip unit electrically connecting to the hard disk drives; wherein the computer system further comprises: a switch unit electrically connecting to the chip unit and the hard disk drives; characterized in that the chip unit is configured to: determine a number of hard disk drives with no boot program among the plurality of hard disk drives; determine a RAID operation mode among the plurality of RAID operation modes based on said number of hard disk drives with no boot program; based on said determination of the RAID operation mode, generate a control signal; and transmit the control signal to the switch unit; wherein the switch unit is configured to: upon receiving the control signal, generate a corresponding setting signal according to the control signal, and transmit the setting signal to the hard disk drives with no boot program, the hard disk drives with no boot program being further configured to: upon receiving the setting signal, switching an operation mode to the determined RAID operation mode. a plurality of hard disk drives, at least one of the hard disk drives containing and executing a boot program normally; a chip unit electrically connecting to the hard disk drives; wherein the computer system further comprises: a switch unit electrically connecting to the chip unit and the hard disk drives; characterized in that the chip unit is configured to: determine a number of hard disk drives with no boot program among the plurality of hard disk drives; determine a RAID operation mode among the plurality of RAID operation modes based on said number of hard disk drives with no boot program; based on said determination of the RAID operation mode, generate a control signal; and transmit the control signal to the switch unit; a switch unit electrically connecting to the chip unit and the hard disk drives; characterized in that the chip unit is configured to: determine a number of hard disk drives with no boot program among the plurality of hard disk drives; determine a RAID operation mode among the plurality of RAID operation modes based on said number of hard disk drives with no boot program; based on said determination of the RAID operation mode, generate a control signal; and transmit the control signal to the switch unit; determine a number of hard disk drives with no boot program among the plurality of hard disk drives; determine a RAID operation mode among the plurality of RAID operation modes based on said number of hard disk drives with no boot program; based on said determination of the RAID operation mode, generate a control signal; and transmit the control signal to the switch unit; wherein the switch unit is configured to: upon receiving the control signal, generate a corresponding setting signal according to the control signal, and transmit the setting signal to the hard disk drives with no boot program, upon receiving the control signal, generate a corresponding setting signal according to the control signal, and transmit the setting signal to the hard disk drives with no boot program, the hard disk drives with no boot program being further configured to: upon receiving the setting signal, switching an operation mode to the determined RAID operation mode.