Abstract: Space is allocated on data storage devices in proportion to weights associated with the storage devices. The weights can be dynamically adjusted at any time in order to accommodate changes in the system and to better utilize the storage devices. The technique used to perform the allocating is independent of the weights used by the allocating. Further, the allocation technique can accommodate general purpose data streams having varying lengths and/or varying access patterns, as well as special purpose data streams, such as video streams.

Abstract: The decision to prefetch inodes is based upon the detecting of access patterns that would benefit from such a prefetch. Once the decision to prefetch is made, a plurality of inodes are prefetched in parallel. Further, the prefetching of inodes is paced, such that the prefetching substantially matches the speed at which an application requests inodes.

Abstract: Space is allocated on data storage devices in proportion to weights associated with the storage devices. The weights can be dynamically adjusted at any time in order to accommodate changes in the system and to better utilize the storage devices. The technique used to perform the allocating is independent of the weights used by the allocating. Further, the allocation technique can accommodate general purpose data streams having varying lengths and/or varying access patterns, as well as special purpose data streams, such as video streams.

Abstract: A system for balancing multiple memory buffer sizes includes a memory partitioned into a plurality of subgroups, each subgroup containing similarly sized buffers. The system further includes a memory manager which manages requests for buffer space by storing and accessing buffer steal history records in a buffer steal history queue.

Abstract: File system backups are carried out by first generating a list of inodes including associated inode numbers in inode number order that have changed since the last backup operation. A table which has file names and inode numbers for all of the files currently in the file system is also generated. This list is sorted by inode number and the table and list are merged to provide a structure for determining which files are to be backed up. This means that relevant inodes and file names are now provided in a single entity. It is also noted that the structure that results from the merge operation is particularly suitable for being read in blocks which thus permits the backup operation to be carried out in parallel. The task of backing up files is also preferably partitioned by file size or other criteria as opposed to being partitioned simply by the number of files assigned to be backed up by any one processor in a distributed or parallel data processing system.

Abstract: A system, method and computer readable medium for providing a writable file system snapshot with ditto address feature is disclosed. In an embodiment of the present invention, the method includes accessing a first file system snapshot in a set of file system snapshots. A snapshot includes data contents comprising at least one shadow inode or at least one shadow inode and at least one data block corresponding to the shadow inode. The data contents of the first snapshot are copied and written to the next oldest file system snapshot. Subsequently, the data contents of the first snapshot are modified in accordance with modifications to at least one source file corresponding to the first snapshot. Then, a next most recent file system snapshot is accessed. The data contents of the next most recent snapshot are copied and written to the first file system snapshot.

Abstract: A system, method and computer readable medium for providing a file system snapshot with ditto address feature is disclosed. The method includes generating a file system snapshot wherein the snapshot is substantially empty. When metadata associated with a source file included in the snapshot is modified, the inode corresponding to the source file is copied to a shadow inode in the snapshot. When information is appended to a data block associated with a source file included in the snapshot, the inode corresponding to the source file is also copied to a shadow inode in the snapshot. When information in a data block associated with a source file included in the snapshot is overwritten or deleted, the inode corresponding to the source file is copied to a shadow inode in the snapshot and the original data block corresponding to the source file is copied to the snapshot.

Abstract: The decision to prefetch inodes is based upon the detecting of access patterns that would benefit from such a prefetch. Once the decision to prefetch is made, a plurality of inodes are prefetched in parallel. Further, the prefetching of inodes is paced, such that the prefetching substantially matches the speed at which an application requests inodes.

Abstract: Space is allocated on storage devices in proportion to weights associated with the storage devices. The space is allocated by a plurality of file systems. In particular, space may be allocated on any one of the devices by one or more of the file systems. The weights can be dynamically adjusted at any time in order to accommodate changes in the system and to better utilize the storage devices. However, since more than one file system may be allocating space on one or more of the storage devices, changes in the weights are propagated to the various file systems that may utilize the information.

Abstract: File system backups are carried out by first generating a list of inodes including associated inode numbers in inode number order that have changed since the last backup operation. A table which has file names and inode numbers for all of the files currently in the file system is also generated. This list is sorted by inode number and the table and list are merged to provide a structure for determining which files are to be backed up. This means that relevant inodes and file names are now provided in a single entity. It is also noted that the structure that results from the merge operation is particularly suitable for being read in blocks which thus permits the backup operation to be carried out in parallel. The task of backing up files is also preferably partitioned by file size or other criteria as opposed to being partitioned simply by the number of files assigned to be backed up by any one processor in a distributed or parallel data processing system.

Abstract: Space is allocated on data storage devices in proportion to weights associated with the storage devices. The weights can be dynamically adjusted at any time in order to accommodate changes in the system and to better utilize the storage devices. The technique used to perform the allocating is independent of the weights used by the allocating. Further, the allocation technique can accommodate general purpose data streams having varying lengths and/or varying access patterns, as well as special purpose data streams, such as video streams.

Abstract: Concurrent access to data is managed through concurrency control techniques. Various types of techniques are employed to manage the access, including locking-based techniques and non-locking-based techniques. A dynamic switch from one type of concurrency control technique (e.g., a locking-based technique) to a different type of concurrency control technique (e.g., a non-locking-based technique) is enabled. This switching is based on access patterns and/or application requirements for each file. The switching allows enhanced performance for both coarse-grain sharing and fine-grain sharing of data.

Abstract: A system, method and computer readable medium for providing a writable file system snapshot with ditto address feature is disclosed. In an embodiment of the present invention, the method includes accessing a first file system snapshot in a set of file system snapshots. A snapshot includes data contents comprising at least one shadow inode or at least one shadow inode and at least one data block corresponding to the shadow inode. The data contents of the first snapshot are copied and written to the next oldest file system snapshot. Subsequently, the data contents of the first snapshot are modified in accordance with modifications to at least one source file corresponding to the first snapshot. Then, a next most recent file system snapshot is accessed. The data contents of the next most recent snapshot are copied and written to the first file system snapshot.

Abstract: A system, method and computer readable medium for providing a file system snapshot with ditto address feature is disclosed. The method includes generating a file system snapshot wherein the snapshot is substantially empty. When metadata associated with a source file included in the snapshot is modified, the inode corresponding to the source file is copied to a shadow inode in the snapshot. When information is appended to a data block associated with a source file included in the snapshot, the inode corresponding to the source file is also copied to a shadow inode in the snapshot. When information in a data block associated with a source file included in the snapshot is overwritten or deleted, the inode corresponding to the source file is copied to a shadow inode in the snapshot and the original data block corresponding to the source file is copied to the snapshot.

Abstract: This invention provides a defragmentation utility that works on-line in parallel with other file system activities. Thus, it avoids making the file system unavailable for periods of time which would, if not for this invention, slow down data communication exchange and the execution of other tasks dependent upon the data. In particular, this invention, steps through all of the valid inodes finding each of the fragments. The defragmentation engine decides which fragments must remain in their current location and which fragments should migrate to another disk block sub-block location. Since the data blocks span across multiple disks, for each valid disk of the file system a set of disk blocks are constructed that are chosen to be filled, herein called plates. When the plates become full or reach a certain fullness, they are removed from the set and replaced by other disk blocks. When a disk block is removed from the plate set, it is moved to a “done” list as it is considered “full”.

Abstract: A system and method are provided that is used by software implemented Redundancy Array of Inexpensive Disk (RAID) arrays to achieve adequate performance and reliability, as well as to improve performance or low cost hardware Raids. The enhancements to the basic RAID implementation speeds up recovery time for software RAIDS. A method is provided for storing data in an array of storage devices. A plurality of block locations on the storage devices are logically arranged as a parity group wherein a parity block stored in a block location as part of a parity group is logically derived from the combination of data blocks stored in the parity group, and each block in a parity group is stored on a different storage device. A plurality of parity groups are grouped into a parity group set. A request is received to write a new data block location on a storage device. The old data block stored at the block location is read. The new data block is written to the block location.