Abstract: A method and a computer system for asymmetric replication of data are provided. Storage of a set of data is organized as a first copy and as a second copy in non-volatile storage. The second copy is reliable and stored so as to be readable at a speed slower than for the first copy. A read instruction regarding the set of data is received and performed preferentially via the first copy such that the asymmetric replication achieves enhanced performance speed. A request to execute a write operation is received. The write operation is executed to the first copy and to the second copy. In response to determining that the write operation to the first copy was unsuccessful, a label for the first copy is set as stale.

Abstract: A method and a computer system for asymmetric replication of data are provided. Storage of a set of data is organized as a first copy and as a second copy in non-volatile storage. The second copy is reliable and stored so as to be readable at a speed slower than for the first copy. A read instruction regarding the set of data is received and performed preferentially via the first copy such that the asymmetric replication achieves enhanced performance speed. A request to execute a write operation is received. The write operation is executed to the first copy and to the second copy. In response to determining that the write operation to the first copy was unsuccessful, a label for the first copy is set as stale.

Abstract: A computer-implemented method includes using a cache replacement algorithm to forcefully evict target data from a cache. Using the cache replacement algorithm includes selectively accessing data in the cache. A computer program product includes one or more computer readable storage media and program instructions collectively stored on the one or more computer readable storage media. The program instructions include program instructions to perform the foregoing method. A system includes a processor and logic integrated with the processor, executable by the processor, or integrated with and executable by the processor. The logic is configured to perform the foregoing method.

Abstract: A computer-implemented method includes using a cache replacement algorithm to forcefully evict target data from a cache. Using the cache replacement algorithm includes selectively accessing data in the cache. A computer program product includes one or more computer readable storage media and program instructions collectively stored on the one or more computer readable storage media. The program instructions include program instructions to perform the foregoing method. A system includes a processor and logic integrated with the processor, executable by the processor, or integrated with and executable by the processor. The logic is configured to perform the foregoing method.

Abstract: Embodiments of the invention relate to accessing data that spans multiple storage devices in a storage system. A first index records identifiers of data blocks and their storage locations, and a second index records storage locations. An update request is processed by writing multiple copies of a received data block identifier and the updated data block to storage locations recorded in the second index. A read request is processed by performing a quorum read of the storage locations recorded in the second index to retrieve the updated data blocks. The processing of the read request also includes performing a quorum read of the first index to determine storage locations that contain data blocks to be read as part of processing the read request. The data blocks to be read exclude the updated data blocks.

Abstract: Embodiments of the invention relate to calculation of error rate for data storage which includes determining a completion status of a read operation of data stored in a storage device, the completion status being one of at least partially complete or not complete. The fault monitoring count is incremented based on the completion status being not complete. The fault monitoring count is decreased based on the completion status being at least partially complete. The fault monitoring count being decreased according to a value based on the number of bytes successfully read. The error rate indicator value is being calculated based on an exponential decay rate related to the number of bytes read. The fault monitoring count threshold is monitored every time the fault monitoring count is incremented and the storage device is identified as faulty once the threshold limit is exceeded.

Abstract: A data validation method comprises associating a validation chunk with one or more data chunks stored on one or more storage mediums. The validation chunk comprises validation information for verifying whether data recorded in a subdivision of the one or more data chunks is lost. A request is received for an operation to be performed on first data stored in a first subdivision of a first data chunk from among said one or more data chunks. One or more portions of the validation information are examined to determine whether the data recorded in said first subdivision is deemed to be lost.

Abstract: Embodiments of the invention relate to calculation of error rate for data storage which includes determining a completion status of a read operation of data stored in a storage device, the completion status being one of at least partially complete or not complete. The fault monitoring count is incremented based on the completion status being not complete. The fault monitoring count is decreased based on the completion status being at least partially complete. The fault monitoring count being decreased according to a value based on the number of bytes successfully read. The error rate indicator value is being calculated based on an exponential decay rate related to the number of bytes read. The fault monitoring count threshold is monitored every time the fault monitoring count is incremented and the storage device is identified as faulty once the threshold limit is exceeded.

Abstract: Embodiments of the invention relate to accessing data that spans multiple storage devices in a storage system. A first index records identifiers of data blocks and their storage locations, and a second index records storage locations. An update request is processed by writing multiple copies of a received data block identifier and the updated data block to storage locations recorded in the second index. A read request is processed by performing a quorum read of the storage locations recorded in the second index to retrieve the updated data blocks. The processing of the read request also includes performing a quorum read of the first index to determine storage locations that contain data blocks to be read as part of processing the read request. The data blocks to be read exclude the updated data blocks.

Abstract: This disclosure relates to parity declustered storage device arrays having partition groups. In an exemplary embodiment, the storage system includes a storage device array, such as disk array. Each storage device is divided into partitions. Each partition includes stripe units, such as hundreds or thousands of stripe units in exemplary embodiments. The storage system also includes a physical array controller coupled to the storage device array. In an exemplary embodiment, the array controller includes a partition group lookup table and stores and retrieves data and parity in the storage devices based on the partition group lookup table. In this exemplary embodiment, the array controller also includes a stripe lookup table and/or a log. In an exemplary embodiment, the partition group lookup table and the stripe lookup table take up less memory (e.g., by an order of magnitude) than a single-level stripe map conveying the same information.

Abstract: This disclosure relates to parity declustered storage device arrays having partition groups. In an exemplary embodiment, the storage system includes a storage device array, such as disk array. Each storage device is divided into partitions. Each partition includes stripe units, such as hundreds or thousands of stripe units in exemplary embodiments. The storage system also includes a physical array controller coupled to the storage device array. In an exemplary embodiment, the array controller includes a partition group lookup table and stores and retrieves data and parity in the storage devices based on the partition group lookup table. In this exemplary embodiment, the array controller also includes a stripe lookup table and/or a log. In an exemplary embodiment, the partition group lookup table and the stripe lookup table take up less memory (e.g., by an order of magnitude) than a single-level stripe map conveying the same information.

Abstract: A data validation method comprises associating a validation chunk with one or more data chunks stored on one or more storage mediums. The validation chunk comprises validation information for verifying whether data recorded in a subdivision of the one or more data chunks is lost. A request is received for an operation to be performed on first data stored in a first subdivision of a first data chunk from among said one or more data chunks. One or more portions of the validation information are examined to determine whether the data recorded in said first subdivision is deemed to be lost.

Abstract: Two methods (native and clone) are used for installing software, such as an operating system, on client system(s) booting from shared storage. The native installation method configures an interconnection network to create an exclusive communication zone between the client system and the shared storage system and installs the operating system on the client system using the exclusive communication zone. After the software is installed, the method terminates the exclusive communication zone. The clone installation method utilizes a point-in-time copy feature of the shared storage system to clone an operating system drive instantaneously. After the drive is cloned, it is logically attached to a new client and the operating system is customized for that client.

Abstract: A multi-fan apparatus and method incorporates mutual active cancellation of fan noise and/or vibrations. The multi-fan apparatus includes two or more fans circuits, each comprising a fan, a fan speed controller and a separate tachometer, and a fan phase controller. The phase controller is connected to at least one fan speed controller and to each tachometer. Each fan's speed is independently and dynamically maintained at the same set speed by the fan speed controllers using an independent control loops. A noise and/or vibration cancellation phase difference between fans is determined in order to achieve destructive interference of pressure waves and, thus, noise and/or vibration reduction, in pre-determined region of a system incorporating the multi-fan apparatus. The phase controller establishes and maintains this cancellation phase difference between the fans based upon feedback from the tachometers.

Abstract: A method and system for asserting a lock in a distributed file system is provided. All distributed locks have a lease for a limited time period, wherein the lease may be renewed periodically. A lock manager data structure is provided to maintain mode compatibility of locks granted to different client nodes for the same object. The process of acquiring or reasserting a lock includes determining whether there are other valid locks in use, as well as whether a valid lock is in operation in a conflicting or compatible mode with a requested lock. A new lock lease may be granted and a lock lease which has expired may be reasserted if a conflicting lease is not present.

Abstract: A method and system for asserting a lock in a distributed file system is provided. All distributed locks have a lease for a limited time period, wherein the lease may be renewed periodically. A lock manager data structure is provided to maintain mode compatibility of locks granted to different client nodes for the same system object. The process of acquiring (60) or reasserting (140) a lock includes determining whether there are other valid locks in use, as well as whether a valid lock is operation in a conflicting or compatible mode with a requested lock (86, 166). A new lock lease maybe granted (120) and a lock lease which has expired may be reasserted (172) if a conflicting lease is not present.

Abstract: In a multiprocessor system, a method for dynamically establishing an I/O path between a processor node and an I/O device for routing data there between. The method starts with providing a configuration graph. The graph has objects associated with elements (devices) of the system and links connecting the objects. The node is identified, and links are then followed in the graph from an object associated with the I/O device to an object associated with a node. If multiple I/O paths exist and an optimal path is desired, the method includes providing in the links routing information containing nodes that can be directly reached via the link. Links are then followed, if possible, whose routing information contains the identified node. If no link having such routing information exists at an object along the path, then another link is chosen having routing information containing another node. This other link may be chosen in a round robin manner if there are multiple links to choose from.

Abstract: A method for configuring devices within a computer system provides device configuration information for types of devices that may be included within the computer system. The device configuration information for a device type includes interface types by which devices of that device type connect to other devices. The method includes determining the interface types of a current object associated with a device. Device types that can exist on a determined interface type of the current object are probed for. A child object is created for a device found from the probing and a link between the current object and the child object is also created. A child object is then made the current object, and the above actions are repeated at least until the devices to be configured within the system have associated objects linked together.