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: The determination of node and/or adapter liveness in a distributed network data processing system is carried out via one messaging protocol that can be assisted by a second messaging protocol which is significantly less susceptible to delay, especially memory blocking delays encountered by daemons running on other nodes. The switching of protocols is accompanied by controlled grace periods for needed responses. This messaging protocol flexibility is also adapted for use as a mechanism for controlling the deliberate activities of node addition (birth) and node deletion (death).

Abstract: The determination of node and/or adapter liveness in a distributed network data processing system is carried out via one messaging protocol that can be assisted by a second messaging protocol which is significantly less susceptible to delay, especially memory blocking delays encountered by daemons running on other nodes. The switching of protocols is accompanied by controlled grace periods for needed responses. This messaging protocol flexibility is also adapted for use as a mechanism for controlling the deliberate activities of node addition (birth) and node deletion (death).

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: During file backup to an off-line storage facility, attributes are included which facilitate the placement of the file into a proper pool during a subsequent restoration operation. This avoids multiple data transfers that may have otherwise been occasioned as a result of improper pool selection during the restore due to the loss or to the unavailability of necessary file attributes when the file was restored.

Abstract: Asynchronous messages are used to prefetch and/or relinquish tokens used in providing locking of shared resources. A message is sent to prefetch one or more tokens, and prior to receiving a reply for the message, another message (e.g., an acquire) is sent for at least one of those tokens. Similarly, a message is sent indicating a voluntary relinquish of one or more tokens and without having acknowledgment that the relinquish request was processed, a further message (e.g., an acquire) is sent for at least one of the tokens. Multiple tokens may be acquired and/or relinquished in a single message to the token server. This reduces message delays and overall message traffic.

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: File system restoration is made more flexible through the use of indicators of individual file restoration status throughout the restoration process. Such indicators are particularly useful in the restoration of large file systems where, for example, the number of files may range upwards of several hundred million. Since file system restoration for large systems takes such a relatively long time, the present invention provides various degrees of individual file access even as the restoration process is being carried out. During file system restoration times, file access may be full or limited to a file's attributes. Most advantageously, the present invention is capable of providing full, dynamically driven (on-demand) file access even during file system restoration operations.

Abstract: A system, method and computer readable medium for providing dynamic links to file system snapshots is disclosed. A link corresponding to a file system inode is generated. Upon activation of the link, the snapshot identifier of the most recent snapshot is retrieved and the most recent snapshot is identified. If the most recent snapshot includes an inode corresponding to the file system inode and the file system inode includes a disk address, then the data block referenced by the disk address is retrieved. If the most recent snapshot includes an inode corresponding to the file system inode and the file system inode includes a ditto disk address (or the inode corresponding to the file system inode is not included), then the inode corresponding to the file system inode indicated in the link is retrieved and the data block corresponding to the file system inode is retrieved.

Abstract: The determination of node and/or adapter liveness in a distributed network data processing system is carried out via one messaging protocol that can be assisted by a second messaging protocol which is significantly less susceptible to delay, especially memory blocking delays encountered by daemons running on other nodes. The switching of protocols is accompanied by controlled grace periods for needed responses. This messaging protocol flexibility is also adapted for use as a mechanism for controlling the deliberate activities of node addition (birth) and node deletion (death).

Abstract: A system, method and computer readable medium for providing a snapshot of a subset of a file system. A first snapshot of a first set of source files in a file system is generated. The first snapshot includes an inode corresponding to each source file in the first set of files. Stored in each inode is a first identifier associated with the first set of files and a second identifier associated with the time of the first snapshot. Next, a second snapshot of a second set of source files is taken. The second snapshot includes an inode corresponding to each source file in the second set of files. Stored in each inode are a first identifier and a second identifier. Subsequent snapshots are taken every first period and every second period for the first set of files and the second set of files, respectively.

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: The amount of memory being utilized to store token state information is monitored. In response to the monitoring, one or more actions are taken. For instance, if the monitoring indicates that too much memory is being used to store token state information, then one or more actions are performed to reclaim memory and/or obtain additional memory elsewhere. These actions may include informing one or more clients to reduce their cache sizes, thereby relinquishing tokens; reducing or eliminating one or more byte range token trees; and/or migrating the token server from one node to another node. If the monitoring indicates that additional memory can be used for storing token state information, then one or more client nodes are informed that their cache sizes can be increased.

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 present invention is directed to a method for controlling file access in a multinode, shared storage, data processing system in which a one set of nodes is capable of acting as metadata controllers and a second set of nodes are tuned for running user applications. By providing two kinds of locks operative at the file level of granularity, a mechanism is produced which permits application programs to also run on their set of metadata controller nodes. One of the locks permits read and write access to existing data blocks but precludes operations such as file deletion or file truncation. The other lock is of lower authority and permits metadata controller nodes, which can provide time limited permissions to the application nodes, to withhold locks which authorize access when requests for access are made from application nodes.

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: A system, method and computer readable medium for providing a standby file system with snapshot feature is disclosed. A first snapshot of a primary file system is generated. Next, a standby file system restores the first snapshot of the primary file system in the standby file system and a snapshot of the standby file system is taken. Then, a second snapshot of the primary file system is taken and a data set capturing the differences between the first snapshot of the primary file system and a previous data set of the primary file system is generated. Subsequently, the data set is applied to the standby file system. Upon unavailability of the primary file system, the standby file system is initialized as the new primary file system. Upon recovery of the old primary file system, the old primary file system is initialized as a new standby file system.

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.