Techniques for mitigating effects of small unaligned writes

摘要

Embodiments are directed to techniques for allowing write operations to proceed on units smaller than a block. Merely decreasing the block size is not desirable, however, since many files are written in large chunks at once, and larger block sizes can increase speed and decrease the amount of overhead metadata required. Therefore, in order to maintain large block sizes while still obtaining the benefit of being able to make small writes when necessary, blocks may be divided into sub-blocks. Unaligned writes that do not fill up an entire block may be segregated and stored separately from aligned writes, the unaligned writes having finer granularity. These techniques may result in faster operation for unaligned writes. They also especially benefit systems using compression because they allow efficiently partially overwriting compressed blocks.