Abstract: Described is a technology by which a virtual machine may be safely migrated to a computer system with a different platform. Compatibility of the virtual machine may be checked by comparing the virtual machine's capabilities against those of the new platform. To ensure compatibility, when created the virtual machine may have its capabilities limited by the lowest common capabilities of the different platforms available for migration. Computer systems may be grouped into migration pools based upon similar capabilities, and/or a virtual machine may be mapped to certain computer systems based upon capabilities needed by that virtual machine, such as corresponding to needed performance, fault tolerance and/or flexibility.

Abstract: Described is a technology by which a virtual machine may be safely migrated to a computer system with a different platform. Compatibility of the virtual machine may be checked by comparing the virtual machine's capabilities against those of the new platform. To ensure compatibility, when created the virtual machine may have its capabilities limited by the lowest common capabilities of the different platforms available for migration. Computer systems may be grouped into migration pools based upon similar capabilities, and/or a virtual machine may be mapped to certain computer systems based upon capabilities needed by that virtual machine, such as corresponding to needed performance, fault tolerance and/or flexibility.

Abstract: Described is a technology by which a virtual machine may be safely migrated to a computer system with a different platform. Compatibility of the virtual machine may be checked by comparing the virtual machine's capabilities against those of the new platform. To ensure compatibility, when created the virtual machine may have its capabilities limited by the lowest common capabilities of the different platforms available for migration. Computer systems may be grouped into migration pools based upon similar capabilities, and/or a virtual machine may be mapped to certain computer systems based upon capabilities needed by that virtual machine, such as corresponding to needed performance, fault tolerance and/or flexibility.

Abstract: Described is a technology by which a virtual machine may be safely migrated to a computer system with a different platform. Compatibility of the virtual machine may be checked by comparing the virtual machine's capabilities against those of the new platform. To ensure compatibility, when created the virtual machine may have its capabilities limited by the lowest common capabilities of the different platforms available for migration. Computer systems may be grouped into migration pools based upon similar capabilities, and/or a virtual machine may be mapped to certain computer systems based upon capabilities needed by that virtual machine, such as corresponding to needed performance, fault tolerance and/or flexibility.

Abstract: Selected server operations that affect objects in a distributed computing system can be off-loaded from servers at which the objects are stored to other servers without the requirement of vertical partitioning of the affected objects and without off-loading entire affected objects. A client environment process that requests an operation on an object is notified of a task server to which selected off-load operations should be sent. The client preferably stores the task server identifier and thereafter sends such operation request directly to the identified task server. The object metadata information can be stored in the client environment, if desired. The object metadata at the owning repository server is maintained, if affected by the requested operation. A single task server can perform off-loaded functions from several other repository servers at the same node and at other nodes, and in that way reduce the workload of many servers.

Abstract: A client-server distributed computer processing system provides staged byte range locking with three levels of lock complexity and contention. When locking activity for a data object involves a plurality of clients, locking is managed centrally in the server operating environment. When only a single client is involved in requesting a lock on a data object such as a data file or portion of a data file, the requesting client can be permitted to manage the locking locally in the requesting client operating environment. Client-managed locking involves two stages of locking complexity on an object-by-object basis. The first stage of client locking involves only a log of current lock activity and handles relatively simple locking. When locking becomes more complex, the client locking is migrated to a second local locking stage, where more complex data structures can support lock fragmentations that affect various portions of the data object, such as partially overlapped byte ranges.

Abstract: A client/server computer system manages shared files. A client includes a data cache and an associated cache manager, and executes a client application that requests data from a shared file. In response to the request, the client cache manager determines if the data is currently stored in the data cache, and if so, grants the client access to the data in the cache. However, if the data is not currently stored in the cache, the client cache manager sends to the server a request for multiple consecutive blocks of data beginning with the first block containing the data requested by the client from the shared file. The server includes a token manager which receives the request, and in response (a) awards the token for a first data block specified in the request regardless of contention for the first data block and (b) awards tokens for all other consecutive blocks following the first block of the multiple blocks held by a client who also holds the token for the first block.

Abstract: A system and method efficiently manage clones of an object group. A base storage area contains metadata for each of multiple objects in the object group. The metadata for each object identifies data within each object. The system receives a request to clone a base storage area, and in response, the system creates a clone storage area containing an identification of the base storage area but not the metadata. If there is a subsequent request to update a portion of one of the objects, then the system copies the portion, copies the metadata into the clone storage area for the one object, makes the update to the object copy and changes the metadata in the base storage area to identify the portion copy instead of the original portion. If there is no subsequent request to update any of the multiplicity of objects, then the system does not copy the metadata for any of the multiplicity of objects into the clone storage area.

Abstract: A method of and system for optimizing process utilization in a shared resource environment that avoids holding system processes while requests are queued or waiting for system resources. Information about a waiting request is retained in control structures; then the same process that frees a resource is utilized to respond to queued requests for that resource. The effect is to minimize the retention and/or allocation of processes and their associated system resource requirements. The same method is applied to the synchronization of interprocess communications.

Abstract: A computer system manages first and second different file systems. The system comprises first and second, different file managers having first and second different APIs for the first and second file systems, respectively. The system also comprises a hybrid file manager for managing the second file system based on requests made using the first API. The hybrid manager applies rules from both APIs to control atomicity of requests, access concurrency, and data consistency rules. The hybrid rules prevent violation of the rules of either API.

Abstract: A file management and backup system manages access to data objects such as records stored in a primary repository, and occasionally backs-up the data objects to a backup repository. A backup utility within the system, periodically or at the request of a user, makes a backup request to a file manager, and specifies the scope of the backup. In response, the file manager makes an entry in a "backup in progress" table indicating that the corresponding file space(s), directory(ies), file(s) and/or data object(s) are currently involved in a consistent backup procedure. Then, the backup utility commences the actual copying of the data within the backup scope to the backup repository with assistance from the file manager in accessing the data from the primary repository.