Control apparatus and method, and storage apparatus

A control method for controlling data access to a storage medium, the control method comprising:

• producing, by a computer, a bitmap in a memory of the computer, the bitmap including a plurality of bits corresponding to different blocks in the storage medium;
• receiving, by the computer, a write request from an access requesting apparatus;
• setting, by the computer when the received write request specifies a data block to be written a number of times to a series of blocks in the storage medium, a series of bits in the bitmap to indicate which blocks in the storage medium the specified data block is to be written;
• determining, by the computer, whether the specified data block is a zero data block containing only zeros or a non-zero data block containing non-zero data;
• setting, by the computer, when the data block is determined to be a zero data block, zero data identification information in the memory to indicate that the data block in the write request is a zero data block, and sending the access requesting apparatus a completion notice of the write request upon completion of the setting of the zero data identification information;
• and
• writing, when the specified data block in the write request is determined to be a non-zero data block, the specified data block to one block of the cache area which corresponds to a topmost one of the series of bits being set in the bitmap, and sending the access requesting apparatus a completion notice of the write request upon completion of the writing the specified data block to the one block of the cache area.

A storage apparatus comprising:

• a storage medium;
• and
• a control apparatus that controls data access to the storage medium, wherein the control apparatus includes:
• a memory configured to store zero data identification information and a bitmap including a plurality of bits corresponding to different blocks in the storage medium, the memory further providing a cache area to temporarily store data to be written to specified blocks in the storage medium, and
• one or more processors configured to perform a procedure comprising:
• receiving a write request from an access requesting apparatus,
• setting, when the received write request specifies a data block to be written a number of times to a series of blocks in the storage medium, a series of bits in the bitmap to indicate which blocks in the storage medium the specified data block is to be written,
• determining whether the specified data block is a zero data block containing only zeros or a non-zero data block containing non-zero data,
• setting, when the data block in the write request is determined to be a zero data block, the zero data identification information in the memory to indicate that the data block in the write request is a zero data block, and sending the access requesting apparatus a completion notice of the write request upon completion of the setting of the zero data identification information, and
• writing, when the specified data block in the write request is determined to be a non-zero data block, the specified data block to one block of the cache area which corresponds to a topmost one of the series of bits being set in the bitmap, and sending the access requesting apparatus a completion notice of the write request upon completion of the writing the specified data block to the one block of the cache area.