Abstract: A data storage methodology wherein a hashing algorithm is applied to break a directory object experiencing frequent concurrent accesses from a number of client or manager applications into a predetermined number of hash component objects and a hash master object that manages the component objects. The hash master object and the hash components, together, constitute a hash directory, which replaces the original non-hashed directory object. Each hash component object contains a portion of the entries contained in the original directory object. Each hash component is managed by only one file manager. The entries in the original directory object are distributed among the hash component objects using a predefined hashing algorithm. The creation of hash components and the hash master allows more than one client application or file manager to concurrently write corresponding hash components without the need for access coordination on each access.

Abstract: In a file system recovery (FSRC) process, an FSRC module performs dynamic checks on file system objects to verify parent-child relationships among various objects in the system. The FSRC module stores a list of objects in the system and relevant object-related information for each object in a memory. A dynamic check on each listed object is then performed using the object-related information to verify parent-child relationships for that object. After the dynamic check is over, the object is removed from the list and its object-related information is deleted from the memory. Objects in the system may be divided into a number of segments and dynamic checks can be performed—one segment at a time. A link database for segment X keeps links (forward or backward pointers) from segments Y (Y≠X) such that the destination object of each link is in segment X.

Abstract: A system and method to perform a system-wide file system image without time smear in a distributed object-based data storage system. A realm manager is elected as an image master using the Distributed Consensus Algorithm to execute image-taking. All pending write capabilities are invalidated prior to taking the system-wide file system image so as to quiesce the realm and prepare the storage system for the system-wide image. Once the system is quiesced, the image master instructs each storage manager in the system to clone each live object group contained therein without explicitly cloning any objects contained in such object group. In one embodiment, a file manager copies an object in the system before a write operation is performed on that object after the image is taken. Neither the cloning operation nor the copying operation update any directory objects in the system. At run time, a client application may use a mapping scheme to access objects contained in the system-wide image.

Abstract: A methodology wherein two different types of locks are used by a storage manager when multiple clients wish to access a particular redundantly-stored file. Simple byte-range based mutual exclusion (or mutex) locks are granted by the storage manager for data writes/updates to the file when the file is in the fault-free state, and individual readers/writers (R/W) locks are granted by the storage manager when the file is in the degraded state. No read locks are required of clients when the file object is in the fault-free state. During the fault-free state of the file object, when exactly one client is writing to the file object, the storage manger grants that file object a whole-file lock valid over the entire file object. Each client may have a client lock manager that interacts with appropriate storage manager lock manager to request and obtain necessary locks. These various locking mechanisms reduce lock-related network traffic in a data storage system.