Patent ID: 7395452

Claim:
A method of preventing data loss during a voluntary disk drive power loss event and an involuntary primary power loss event, the method comprising: supplying write data from a host computer into a volatile write buffer; transferring the write data directly from the volatile write buffer to a disk drive while disk drive power is present; maintaining charge in an energy storage device; supplying electrical power from the energy storage device upon detection of the involuntary primary power loss event, wherein the electrical power is supplied to at least the volatile write buffer and nonvolatile cache to save the write data to the non-volatile cache in an occurrence of the involuntary primary power loss event; otherwise, moving the write data from volatile buffer into the nonvolatile cache during the voluntary disk drive power loss event while continuing to accept incoming data to the volatile buffer from the host computer; transferring the write data from the nonvolatile cache to the disk drive upon cessation of the voluntary disk drive power loss event, whereby loss of the write data is prevented while the disk drive is temporarily powered down; and wherein data flowing from the volatile write buffer directly into the disk drive bypasses the non-volatile cache while disk drive power is present.