Abstract: A data network links a number of host processors to alternative shared resources. In order to allocate a respective subset of the alternative shared resources to each host, a directory service of the network is programmed to present a respective view of the network to each host. For example, hosts on the same network loop may see a different picture of the network. When a host logs into the network, the directory service reports to the host information about the alternative shared resources that the host should use. The host then commences a sequence of data processing operations during which the host accesses only the shared resources that were reported to it by the directory service. The shared resources, for example, are ports of a storage subsystem, and a respective subset of the ports is assigned to each host to balance loading of the hosts on the ports.

Abstract: A storage controller has at least one physical data port for a data network including host processors. The storage controller is programmed to provide a plurality of virtual ports for access to storage, and a virtual switch for routing storage access requests from the physical port to the virtual ports. The virtual ports and the virtual switch are defined by software. The virtual ports appear to the hosts as physical ports in the data network. For example, in a Fiber-Channel network, the virtual ports have World Wide Names (WWNs) and are assigned temporary addresses (S_Ds), and the virtual switch provides a name server identifying the WWNs and S_IDs of the virtual ports. For convenient partitioning of storage among host processors, one or more virtual ports are assigned to each host, and a set of storage volumes are made accessible from each virtual port. A host can access storage at a virtual port only if the virtual port has been assigned to the host.

Abstract: A method and apparatus for a networked computer system including a plurality of devices and a shared resource. In response to one of the devices attempting to access the shared resource and representing itself to the shared resource as a first device, determining whether the device is attempting to access the shared resource through a physical connection through the network that is different than a physical connection used by the first device to access the shared resource, and when it is, denying the attempted access.

Abstract: A method and apparatus for manipulating data in a storage device that is coupled to a host computer. Manipulations that can be performed by the storage device include moving non-contiguous blocks of data between the host computer and the storage device in a single operation. Other manipulations can be performed directly by the storage device without passing data to or from the host computer and include copying data from one logical object that is defined on the host computer to another, initializing, backing-up, transforming, or securely deleting a logical object that is defined by the host computer with a single command. In one embodiment, an application programming interface is provided that allows a relationship between logical objects on a host computer and storage locations on a storage device to be communicated between the host computer and the storage device.

Abstract: A method and apparatus for accessing storage from at least two different host computers features creating a first file having a first meta-data format and user data blocks in a mass storage medium using the first host computer and reading a logical to physical mapping of the user data blocks from the first file. A second file, having a second meta-data format, is created using a second host computer and the second file has blocks preallocated to be the same length as user data blocks of the first file. A logical to physical mapping of the preallocated user blocks is then obtained and the data blocks of the preallocated file are linked to the data blocks of the first file so that a reference to the preallocated blocks will provide an address at which the data requested can be read in the first file. In this manner, different meta-data blocks, corresponding to different filesystems, and/or operating systems, can be used in the respective first and second host computers.

Abstract: A method and apparatus for managing a log of information in a computer system including a host computer and a storage system that stores data accessed by the host computer. The computer system includes a plurality of logical volumes of data that are visible to the host and the storage system and that are perceived by the host computer as comprising a plurality of raw storage devices. The storage system includes at least one physical storage device and at least one mapping layer that maps the logical volumes to the physical storage device. In one aspect of the invention, the log includes information concerning at least one I/O operation. The information includes a first component relating to aspects of the I/O operation controlled by the host computer and a second component relating to aspects of the I/O operation controlled by the storage system. In one aspect, the host computer stores the log which includes information relating to aspects of the I/O operation controlled by the intelligent storage system.

Abstract: In a data storage subsystem providing data storage to host processors, a process of configuration defines a subset of the data storage that each host may access. A vector specification is a convenient mechanism for specifying a set of storage volumes that a host may access. For example, for each host processor, there is stored in memory of the data storage subsystem a list of contiguous ranges or vectors of the storage volumes that the host may access. To determine whether or not a specified logical volume number is included in the vector, a mudulus of the stride of the vector is computed from the difference between the address of the specified logical volume and the beginning address of the vector, and the modulus is compared to zero. To provide a mapping between logical unit numbers specified by the host and the logical volumes, a contiguous range of logical unit numbers may also be specified for each contiguous range or vector of storage volumes.

Abstract: A method and apparatus for manipulating data in a storage device that is coupled to a host computer. Manipulations that can be performed by the storage device include moving noncontiguous blocks of data between the host computer and the storage device in a single operation. Other manipulations can be performed directly by the storage device without passing data to or from the host computer and include copying data from one logical object that is defined on the host computer to another, initializing, backing-up, transforming, or securely deleting a logical object that is defined by the host computer with a single command. In one embodiment, an application programming interface is provided that allows a relationship between logical objects on a host computer and storage locations on a storage device to be communicated between the host computer and the storage device.

Abstract: A method and apparatus for managing data storage in a computer system including a host computer and a storage system that stores data accessed by the host computer. A performance condition that impacts system performance is detected, and in response thereto, the data within the storage system is reconfigured to improve system performance. In one aspect, this detection and reconfiguration is done automatically within the storage system in a manner transparent to the host computer. Examples of performance conditions that can be detected and alleviated include logical volumes including hot spots that are larger than the cache storage dedicated to the volumes, data segments that are accessed frequently by the host but not sufficiently frequently so that they remain in the cache between accesses, and large data segments that are accessed frequently and sequentially by the host and are stored on the same physical device within the storage system.

Abstract: In a data storage subsystem providing data storage to host processors, a process of configuration defines a subset of the data storage that each host may access. A vector specification is a convenient mechanism for specifying a set of storage volumes that a host may access. For example, for each host processor, there is stored in memory of the data storage subsystem a list of contiguous ranges or vectors of the storage volumes that the host may access. To determine whether or not a specified logical volume number is included in the vector, a modulus of the stride of the vector is computed from the difference between the address of the specified logical volume and the beginning address of the vector, and the modulus is compared to zero. To provide a mapping between logical unit numbers specified by the host and the logical volumes, a contiguous range of logical unit numbers may also be specified for each contiguous range or vector of storage volumes.

Abstract: A storage system is provided that includes a plurality of storage devices and a data structure, accessible to the storage system, that includes a plurality of records corresponding to a plurality of network devices that are coupled to the storage system. Each record includes configuration data that identifies each of the plurality of storage devices to which data access by a respective one of the plurality of network devices is authorized. Each record may further include visibility data that identifies whether certain types of non-data access, such as requests for general information relating to a respective storage device, by a respective one of the plurality of network devices is permitted, even though data access to the respective storage device by the respective one of the plurality of network devices is not authorized.

Abstract: A method of managing information to be stored on a storage disc in a disc drive system to achieve improved system performance. Some of the data on the disc may be mirrored on the same surface of the disc to reduce latency and/or seek time. Compression techniques may be employed to limit reductions in the storage capacity of the disc. In another embodiment, data is preferentially stored on the outer tracks of the disc because system performance is greater when accessing outer tracks. Compression techniques may also be employed with this embodiment to limit reductions in the storage capacity of the disc. Compressed data stored on the disc may be transferred to another storage medium in its raw compressed form to reduce the number of instructions that would be required to transfer the data if it were decompressed before transfer.

Abstract: A method and apparatus for manipulating data in a storage device that is coupled to a host computer. Manipulations that can be performed by the storage device include moving non-contiguous blocks of data between the host computer and the storage device in a single operation. Other manipulations can be performed directly by the storage device without passing data to or from the host computer and include copying data from one logical object that is defined on the host computer to another, initializing, backing-up, transforming, or securely deleting a logical object that is defined by the host computer with a single command. In one embodiment, an application programming interface is provided that allows a relationship between logical objects on a host computer and storage locations on a storage device to be communicated between the host computer and the storage device.

Abstract: A method of managing information to be stored on a storage disc in a disc drive system to achieve improved system performance. Some of the data on the disc may be mirrored on the same surface of the disc to reduce latency and/or seek time. Compression techniques may be employed to limit reductions in the storage capacity of the disc. In another embodiment, data is preferentially stored on the outer tracks of the disc because system performance is greater when accessing outer tracks. Compression techniques may also be employed with this embodiment to limit reductions in the storage capacity of the disc. Compressed data stored on the disc may be transferred to another storage medium in its raw compressed form to reduce the number of instructions that would be required to transfer the data if it were decompressed before transfer.

Abstract: Method and apparatus for detecting changes in a configuration of a computer system including a host computer and at least one computer system resource. Information relating to a reference configuration of the computer system is stored at a first point in time. A current configuration of the computer system is determined at a second point in time. The current configuration of the computer system is compared with the reference configuration to determine whether the current configuration differs from the reference configuration. An indication is provided when the current configuration of the computer system differs from the reference configuration.

Abstract: A data management technique for managing accesses to data at a shared storage system includes a filter at the storage system. The filter is coupled to a configuration table, which identifies which of a number of coupled host processors have accesses to each of the resources at the device. During operation, requests received from the host devices are filtered by the filter, and only those requests to resources that the individual host devices have privilege to access are serviced. Advantageously, data security is further enhanced by authenticating each of the requests received by the storage system to verify that the host processor that is represented as forwarding the request is the indicated host processor. In addition, transfers of data between the storage system and the host processor may be validated to ensure that data was not corrupted during the data transfer.

Abstract: A storage controller for controling access to data storage has a memory and at least one data port for a data network including host processors. The memory is programmed to define a respective specification for each host processor of a respective subset of the data storage to which access by the host processor is restricted, and each specification is associated with a host identifier stored in the memory. When the storage controller receives a data access request from a host processor, it decodes a host identifier from the data access request, and searches the memory for a host identifier matching the host identifier decoded from the request. Upon finding a match, the respective specification of the respective subset for the host processor is accessed to determine whether or not storage specified by the storage access request is contained in the respective subset. If so, then storage access can continue, and otherwise, storage access is denied.

Abstract: A method of providing a lock to a requester, the method including the steps of storing a lock indicator at a storage location on a storage medium; receiving a lock command from a requester on a host computer, wherein the lock command identifies the storage location on the storage medium and represents a lock request; in response to receiving the lock command, retrieving the lock indicator from the storage medium; performing an exclusive OR operation on the lock request and the retrieved lock indicator to produce a lock request result; and sending an indication back to the host computer indicating whether the lock request was granted.

Abstract: Method and apparatus for detecting changes in a configuration of a computer system including a host computer and at least one computer system resource. Information relating to a reference configuration of the computer system is stored at a first point in time. A current configuration of the computer system is determined at a second point in time. The current configuration of the computer system is compared with the reference configuration to determine whether the current configuration differs from the reference configuration. An indication is provided when the current configuration of the computer system differs from the reference configuration.

Abstract: A stacked map storage system has a base mapping of logical data to physical locations in the storage system. Level maps are created either as positive or negative maps of a lower level map. A positive map enables an alternate view while keeping the next lowest level map the same. A negative map allows changes to a lower level map but stores references to the data in itself so the negative map becomes a backup. Negative maps freeze storage in themselves and are read-only. A positive map allows changes to itself and can be used by applications under test to make changes, while not allowing changes to the next lower level map to be made through the positive map. In a preferred embodiment, maps can be stacked to any number of levels, can be shared by applications and hosts, and can either be deleted or merged. Deletion removes the map as though it never existed. A merge overlays an upper view onto a lower view and thus changes the lower view to match the other's state.