A data storage system is an arrangement of hardware and software that typically includes one or more storage processors coupled to an array of non-volatile data storage devices, such as magnetic disk drives, electronic flash drives, and/or optical drives. The storage processors service host input/output (I/O) operations received from host machines. The received I/O operations specify storage objects (e.g. logical disks or “LUNs”) that are to be written to, read from, created, or deleted. The storage processors run software that manages incoming I/O operations and that performs various data processing tasks to organize and secure the host data received from the host machines and stored on the non-volatile data storage devices
Data storage systems commonly arrange data in structures known as filesystems. Such file systems include both data and metadata. The metadata organizes the file data on disk, such that each file's data can be located, placed in proper sequence, and kept separate from other files' data.
Some filesystems employ compression. Compression allows the data within the filesystem to be stored in a reduced amount of space. Compression may be performed “inline” in certain filesystems, allowing data to be stored in compressed form “on-the-fly” as it is received.