Backup method and disk array apparatus

A disk array apparatus comprising:

• a volatile memory for storing cache data;
• a nonvolatile memory;
• and
• a controller that:
• writes the cache data stored in a volatile memory into a selected area of the nonvolatile memory,
• generates parity data by calculating an exclusive OR of each of a plurality of predetermined parts of the cache data in the volatile memory,
• generates a plurality of cyclic redundancy check codes from each of the predetermined parts of the cache data in the volatile memory respectively;
• checks an error of each of the predetermined parts of the cache data in the nonvolatile memory by using the cyclic redundancy check codes;
• verifies whether an error found in a checked part of the cache data in the nonvolatile memory can be recovered by using the parity data;
• rewrites a part of the cache data when the error found in the part of the cache data in the nonvolatile memory cannot be recovered by using the parity data in an area of the nonvolatile memory different from the selected area;
• and
• writes the generated parity data into the nonvolatile memory.

A computer-readable recording medium executing computer program making a backup of cache data of a disk array apparatus to a nonvolatile memory, the cache data being stored in a volatile memory, the program being designed to make a computer perform a process comprising:

• writing the cache data stored in the volatile memory into a selected area of the nonvolatile memory;
• generating parity data by calculating an exclusive OR of each of a plurality of predetermined parts of the cache data in the volatile memory;
• generating a plurality of cyclic redundancy check codes from each of the predetermined parts of the cache data in the volatile memory respectively;
• checking an error of each of the predetermined parts of the cache data in the nonvolatile memory by using the cyclic redundancy check codes;
• verifying whether an error found in a checked part of the cache data in the nonvolatile memory can be recovered by using the parity data;
• rewriting a part of the cache data when the error found in the part of the cache data in the nonvolatile memory cannot be recovered by using the parity data in an area of the nonvolatile memory different from the selected area;
• and
• writing the generated parity data into the nonvolatile memory.