Space allocation in a write anywhere file system

A method for improved space allocation in a write anywhere file system, including a file system having a set of storage blocks in a mass storage system, including

• maintaining a collection of bit maps responsive to the set of storage blocks available for writing data;
• determining, for each one of a plurality of regions of said storage blocks in said mass storage system, a spacemap including an array of binary numbers, each said binary number being count related to a number of blocks available or not available for writing data in one of said regions, wherein said spacemap is responsive to at least two bitmaps included in said collection of bitmaps;
• selecting at least one of said plurality of regions in response to said spacemap;
• and
• writing at least part of a file composed of a collection of file blocks to the selected one of said plurality of regions.

An apparatus for improved space allocation in a write anywhere file system, including a file system that has a set of storage blocks in a mass storage system;

• wherein
• said file system maintains an active map of one of said storage blocks not available to write data;
• said file system records a consistency point which includes a consistent version of said file system at a previous time, said consistency point includes a copy of said active map at said previous time;
• said file system determines, for each one of a plurality of regions of said storage blocks in said mass storage system, a spacemap including an array of binary numbers, each said binary number being count related to a number of blocks available or not available for writing data in one of said regions, wherein said spacemap is responsive to said active map and a summary map;
• and
• said file system selects at least one of said plurality of regions in response to said spacemap.

An apparatus for improved space allocation in a write anywhere file system, including a file system having a set of storage blocks in a mass storage system including

• means for maintaining an active map of said storage blocks not available for writing data;
• means for recording a consistency point including a consistent version of said file system at a previous time, said consistency point including a copy of said active map at said previous time;
• means for determining, for each one of a plurality of regions of said storage blocks in said mass storage system, a spacemap including an array of binary numbers, each said binary number being count related to a number of blocks available or not available for writing data in one of said regions, wherein said spacemap is responsive to said active map and a summary map;
• and
• means for selecting at least one of said plurality of regions in response to said spacemap.

A memory storing information including instruction, the instructions for improved space allocation in a write anywhere file system, including a file system having a set of storage blocks in a mass storage system, the instructions including the steps of

• maintaining an active map of said storage blocks not available for writing data;
• recording a consistency point in said file system including a consistent version of said file system at a previous time, said consistency point including a copy of said active map at said previous time;
• determining, for each one of a plurality of regions of said storage blocks in said mass storage system, a spacemap including an array of binary numbers, each said binary number being count related to a number of blocks available or not available for writing data in one of said regions, wherein said spacemap is responsive to said active map and a summary map;
• and
• selecting at least one of said plurality of regions in response to said spacemap.

A memory storing information including instruction, the instructions for improved space allocation in a write anywhere file system, including a file system having a set of storage blocks in a mass storage system, the instructions including the steps of

• maintaining a collection of bit maps responsive to the set of storage blocks available for writing data;
• determining, for each one of a plurality of regions of said storage blocks in said mass storage system, a spacemap including an array of binary numbers, each said binary number being count related to a number of blocks available or not available for writing data in one of said regions, wherein said spacemap is responsive to at least two bitmaps included in said collection of bitmaps;
• selecting at least one of said plurality of regions in response to said spacemap;
• and
• writing at least part of a file composed of a collection of file blocks to the selected one of said plurality of regions.