A high availability, high reliability storage system (215) that leverages rapid advances in commodity computing devices and the robust nature of internetwork technology such as the Internet (213). A system of parity distribution (505) in accordance with the present invention allows for greater fault tolerance and levels of storage efficiency than possible with conventional RAID (levels 0-5) paradigms. Data can be recovered or made available even in the case of loss of N, N+1, or more devices or storage elements (215) over which stripes of the data set have been distributed or partitioned. The present invention provides a parity distribution that can be used to distribute data stored in a single storage device or across multiple connected or otherwise networked devices.

System and method for data protection with multidimensional parity

In a computer network system, a user-defined file modification request is communicated to a primary server, which communicates the request to a secondary server. The file modification request is saved in a non-volatile storage media associated with the primary server, and the file modification request is executed and saved in a non-volatile storage media associated with the secondary server.

Real time backup system

An on-line services network includes application servers and Gateway microcomputers that are interconnected by a LAN. The Gateway microcomputers receive service requests which are transmitted over a WAN from client microcomputers operated by end users. Upon receiving a request to open a service, the Gateway microcomputers access a periodically-updated service map to locate the replicated application servers that are currently running the corresponding service application, and then apply a load balancing method (using server load data contained within the service map) to select an application server that has a relatively low processing load. A communications protocol between the client and Gateway microcomputers enables users to access multiple services simultaneously. A hot redirection technique allows a user service session to be transferred from one application server to another (replicated) application server without termination of the service session. Various mechanisms are provided for efficiently reallocating application servers to different on-line services, and for allowing additional servers to be efficiently added to the network.

Method of redirecting a client service session to a second application server without interrupting the session by forwarding service-specific information to the second server

Access rights of users of a computer network with respect to data entities are specified by a relational database stored on one or more security servers. Application servers on the network that provide user access to the data entities generate queries to the relational database in order to obtain access rights lists of specific users. An access rights cache on each application server caches the access rights lists of the users that are connected to the respective application server, so that user access rights to specific data entities can rapidly be determined. Each user-specific access rights list includes a series of category identifiers plus a series of access rights values. The category identifiers specify categories of data entities to which the user has access, and the access rights values specify privilege levels of the users with respect to the corresponding data entity categories. The privilege levels are converted into specific access capabilities by application programs running on the application servers.

System and method for controlling access to data entities in a computer network

A network file server includes a first set of data processors for receiving requests from clients, and a second set of data processors for accessing read-write file systems. A respective data processor in the second set is assigned to each file system for exclusive management of locks on the file system. The file server can detect failure of a failed data processor and automatically recover from the failure. When a failure of a data processor in the first set is detected, a spare data processor is programmed with the logical and physical network addresses of the failed data processor so that the spare data processor assumes the network identity of the failed data processor. When a failure of a data processor in the second set is detected, responsibility for management of the locks on each file system managed by the failed data processor is transferred to an operational data processor. Preferably the responsibility is transferred to the operational data processors in such a way as to balance loading on the operational data processors. The data processors can be commodity digital computers for low cost, and a cached disk storage subsystem or file system caches and remote dual copy techniques can be used to ensure high performance and high data availability.

Recovery from failure of a data processor in a network server

An Integrity Server computer for economically protecting the data of a computer network's servers, and providing hot standby access to up-to-date copies of the data of a failed server. As the servers' files are created or modified, they are copied to the Integrity Server. When one of the servers fails, the Integrity Server fills in for the failed server, transparently providing the file service of the failed server to network clients. The invention provides novel methods for managing the data stored on the Integrity Server, so that the standby files are stored on low-cost media such as tape, but are quickly copied to disk when a protected server fails. The invention also provides methods for re-establishing connections between clients and servers, and communicating packets between network nodes, to allow the Integrity Server to stand-in for a failed server without requiring reconfiguration of the network clients.

Stand-in Computer file server providing fast recovery from computer file server failures

An Integrity Server computer for economically protecting the data of a computer network's servers, and providing hot standby access to up-to-date copies of the data of a failed server. As the servers' files are created or modified, they are copied to the Integrity Server. The invention provides novel methods for managing the data stored on the Integrity Server, so that up-to-date snapshots of files of the protected file servers are stored on low-cost media such as tape, but without requiring that a system manager load large numbers of tapes.

Continuously-snapshotted protection of computer files

A data processing system which handles thirty-two bit logical addresses which can be derived from either sixteen bit logical addresses or thirty-two bit logical addresses, the latter being translated into physical addresses by unique translation means. The system includes means for decoding macro-instructions of both a basic and an extended instruction set, each macro-instruction containing in itself selected bit patterns which uniquely identify which type of instruction is to be decoded. The instruction responsive apparatus thereof responds to unique microinstructions which, for example, provide for the selection of one of a plurality of interrupt routines each corresponding to an interrupt request from a different external device, provide for the sequential loading of a plurality of segment identification registers each pointing to selected memory management tables associated with a segment storage region of main memory, provide for a program counter relative jump operation, provide for zero-extending or sign-extending 16-bit words to 32-bit words having the same value, and provide for the multiplication of the lower 16 bits of two 32-bit accumulators and the sign-extension of the 16-bit result to form a 32-bit word.

Data processing system having instruction responsive apparatus for both a basic and an extended instruction set

A data processing system which handles thirty-two bit logical addresses which can be derived from either sixteen bit logical addresses or thirty-two bit logical addresses, the latter being translated into physical addresses by unique translation means. The system includes means for decoding macro-instructions of both a basic and an extended instruction set, each macro-instruction containing in itself selected bit patterns which uniquely identify which type of instruction is to be decoded. The decoded macro-instructions provide the starting address of one or more micro-instructions, which address is supplied to a unique micro-instruction sequencing unit which appropriately decodes a selected field of each micro-instruction to obtain each successive micro-instruction. The system uses hierarchical memory storage using eight storage segments (rings), access to the rings being controlled in a privileged manner according to different levels of privilege. The memory system uses a bank of main memory modules which interface with the central processor system via a dual port cache memory, block data transfers between the main memory and the cache memory being controlled by a bank controller unit.

Data processing system having a unique micro-sequencing system

@ Certain device interrupts, distinguished at XVCT interrupts, are handled using four regions on main memory. The interrupt code is held in two locations (LOC 1, 2) in the first region and the code in the first location (LOC 1) enables an XVCT interrupt to be recognised. The contents of the second location (LOC 2) are then used as a displacement to point to a location in the second region which is an XVCT table with an entry for each interrupting device. These entries in turn point to areas within the third region, a device control table (DCT). Each such area contains firstly a pointer to the interrupt routine (in the fourth memory region) for the device in question, secondly a MASKcode which identifies the other devices which are prevented from interrupting while the device in question is serviced and a processor status register word (PSR) which determines whether or not a fixed point overflow condition is to be enabled. Execution of the selected interrupt routine is preceded by a conventional stack save (PUSH) operation and followed by a restore (POP) operation.

Charles J. Holland

Papers

Stand-in Computer file server providing fast recovery from computer file server failures

Continuously-snapshotted protection of computer files

Data processing system having instruction responsive apparatus for both a basic and an extended instruction set

Data processing system having a unique micro-sequencing system

Data processing system with improved interrupt handling