Efficient access to storage devices with usage bitmaps

A system for presenting values stored in location sets comprising at least two locations of a storage set, the system comprising:

• a usage bitmap generating component configured to, upon receiving an allocation request to generate a storage region in the storage set, generate a usage bitmap indicating, for respective location sets of the storage region, whether values exist in the locations of the location set;
• a parity value generating component configured to, upon receiving a request to write a data value to a data location:
• write the data value to the data location;
• update the usage bitmap to indicate that a data value exists the data location:
• for the location set including the parity location, calculate a parity value for the location set using, for the respective data locations of the location set:
• where the usage bitmap indicates that a data value exists at the data location, the data value stored at the data location;
• and
• where the usage bitmap indicates that a data value does not exist at the data location, a default value for the data location;
• and
• store the parity value at the parity location for the location set.

A computer-readable memory device storing instructions that cause a storage device to fulfill requests to write to a storage set comprising a storage region storing a location set comprising at least two data values respectively stored at a data location of the storage region, and at least one parity value for the at least two data values stored at a parity location, by:

• writing the data value to the data location;
• updating the usage bitmap to indicate that a data value exists at the data location;
• for the location set including the parity location, calculating the parity value using, for the respective data locations of the location set:
• where the usage bitmap indicates that a data value exists at the data location, the data value stored at the data location;
• and
• where the usage bitmap indicates that a data value does not exist at the data location, a default value for the data location;
• and
• writing the parity value at the parity location for the location set.