Managing truncation of files of file systems

#This application is related to co-pending U.S. patent application Ser. No. 14/870,514 entitled MANAGING TRUNCATION OF FILES OF FILE SYSTEMS filed on Sep. 30, 2015, which is incorporated herein by reference.

#This application relates to managing truncation of files of file systems.

#Computer systems may include different resources used by one or more host processors. Resources and host processors in a computer system may be interconnected by one or more communication connections. These resources may include, for example, data storage devices such as those included in the data storage systems manufactured by EMC Corporation. These data storage systems may be coupled to one or more servers or host processors and provide storage services to each host processor. Multiple data storage systems from one or more different vendors may be connected and may provide common data storage for one or more host processors in a computer system.

#Features and advantages of the present invention will become more apparent from the following detailed description of exemplary embodiments thereof taken in conjunction with the accompanying drawings in which:

#FIGS. 1-2 are examples of an embodiment of a computer system that may utilize the techniques described herein;

#FIG. 3 is an example illustrating storage device layout;

#Described below is a technique for use in managing truncation of files of file systems, which technique may be used to provide, among other things, receiving a request to delete a portion of a file of a file system, determining a set of extents associated with the portion of the file identified for deletion, creating a replica of the set of extents, where the replica represents a state of the set of extents at a particular prior point in time, deleting the portion of the file by updating metadata of the file, and asynchronously deleting the replica in background.

#Generally, a storage extent is a logical contiguous area of storage reserved for a user requesting the storage space. A storage extent may include a set of disks having different RAID levels. A disk may be a physical disk within the storage system. A LUN may be a logical unit number which is an identifier for a logical unit representing a portion of disk storage. Each slice of data may have a mapping to the location of the physical drive where it starts and ends. A LUN presented to a host system may be organized as a file system by a file system mapping logic of a storage system.

#A file is uniquely identified by a file system identification number. Each data block of a file is referenced by a logical block number and/or file system block number. A logical block number of a file refers to a data block by relative position of the data block inside the file. A file system block number of a file refers to a data block by relative position of the data block on a physical disk device on which the file is stored. A file system block number for a data block is computed based on a file offset and the size of the data block. Further, an inode of a file includes metadata that provides a mapping to convert a file system block number of a data block to its corresponding logical block number. For example, in case of a data block size of 4 kilobytes (KB), if a file offset value is smaller than 4096 bytes, the file offset corresponds to the first data block of the file, which has file block number 0. Further, for example, if a file offset value is equal to or greater than 4096 bytes and less than 8192 bytes, the file offset corresponds to the second data block of the file, which has file block number 1.