Storage system and method for detecting and utilizing wasted space using a file system
A file system in a storage system can store files received from a host in clusters of memory in the storage system. An end portion of a file may not use the entire cluster. As a result, the end clusters of the stored files can contain unused space. A system and method detects the unused space in such clusters and creates a virtual cluster from the unused space.
1. A storage system comprising:
a memory; and
a controller configured to:
store plurality of files in the memory, wherein storage of the plurality of files results in unused space in a plurality of clusters of memory;
identify the unused space in the plurality of clusters;
in response to the unused space exceeding a threshold, determine whether space is available in a file allocation table for repurposing the unused space in the plurality of clusters; and
in response to determining that space is available in the file allocation table, create a virtual cluster from the unused space in the plurality of clusters.
2. The storage system of claim 1 , wherein the controller is further configured to identify the unused space from a start cluster, an end cluster, and a file size of each of the plurality of files.
3. The storage system of claim 2 , wherein the start clusters and file sizes are stored in directory entries for the plurality of files.
4. The storage system of claim 3 , wherein the directory entries are stored in a root directory, and wherein the controller is further configured to read a boot record to identify a location of the root directory.
5. The storage system of claim 2 , wherein the controller is further configured to identify the end clusters from file allocation structures.
6. The storage system of claim 1 , wherein the controller is further configured to add the identified unused space to a counter.
7. The storage system of claim 6 , wherein the controller is further configured to create the virtual cluster from the unused space in response to a value of the counter reaching a second threshold.
8. The storage system of claim 1 , wherein the controller is further configured to, in response to a command to delete a file of the plurality of files:
determine whether the virtual cluster related to the file contains valid data;
in response to determining that the virtual cluster does not contain valid data, mark the virtual cluster as unavailable; and
in response to determining that the virtual cluster contains valid data, mark an end cluster for the file as unavailable.
9. The storage system of claim 1 , wherein the controller is further configured to use the unused space to improve endurance and/or performance during a memory compaction process.
10. The storage system of claim 1 , wherein the controller is further configured to use the virtual cluster to improve memory yield during a firmware download process.
11. In a storage system comprising a memory, a method comprising:
storing a plurality of files in the memory, wherein storage of the plurality of files consumes some, but not all, memory locations allocated for the plurality of files;
identifying unused space in the memory locations;
in response to the unused space exceeding a threshold, determining whether space is available in a file allocation table for repurposing the unused space in the memory locations; and
in response to determining that space is available in the file allocation table, creating a virtual memory location from the unused space.
12. The method of claim 11 , further comprising identifying the unused space from a start cluster, an end cluster, and a file size of each of the plurality of files.
13. The method of claim 12 , further comprising reading a boot record to identify, a location of a root directory, wherein the root directory stores directory entries that store the start clusters and file sizes.
14. The method of claim 12 , further comprising identifying the end clusters from file allocation structures.
15. The method of claim 11 , further comprising:
adding the unused space to a counter; and
creating the virtual memory location in response to a value of the counter reaching a second threshold.
16. The method of claim 11 , further comprising using the virtual memory location to improve memory yield during a memory compaction process or during a firmware download process.
17. A storage system comprising:
a memory;
means for storing a plurality of files in the memory, wherein storage of the plurality of files results in unused space in a plurality of clusters of memory;
means for identifying the unused space in the plurality of clusters;
means for, in response to the unused space exceeding a threshold, determining whether space is available in a file allocation table for repurposing the unused space in the plurality of clusters; and
means for creating a virtual cluster from the unused space in response to determining that space is available in the file allocation table.
18. The storage system of claim 17 , wherein the unused space is identified from a start cluster, an end cluster, and a file size of each of the one or more files.
19. The storage system of claim 18 , wherein the end clusters are stored in file allocation structures, wherein the start clusters and file sizes are stored in directory entries for the one or more files, wherein the directory entries are stored in a root directory, and wherein a location of the root directory is identified in a boot record.
20. The storage system of claim 17 , further comprising means for adding the unused space to a counter, wherein the virtual cluster is created after a value of the counter reaches a second threshold.