Paragraph Number

245

File systems may write zeros to unused blocks to indicate that the blocks do not hold data that needs to be preserved and/or for security reasons. Empty-block directives or hints sent by the file system may be used in place of these operations. In some embodiments, a data segment token may be stored in place of the sequence of zeros (or other data pattern) to signify that the blocks are not in use. This may be especially useful in block storage applications. Blocks are always considered valid, their contents needing to be preserved, even if the client (e.g., file system) is not currently using the blocks to store valid data. Many file systems are diligent about zeroing out blocks that are not actually storing valid data. The blocks may be zeroed out for security reasons (e.g., prevent read before write hazards). The compression module described above may be used to reduce the storage requirements of these types of sequences. Alternatively, or in addition, an API may be provided to identify unused blocks (e.g., an API to “throw away the contents of these blocks” or a “clear” command). Subsequent requests to read data of such blocks may return zeros.

Added by DJM 3 2021