Abstract: An apparatus, system, and method are disclosed for efficiently verifying writes. A storage module stores a plurality of data sets in a storage controller memory. A write module writes the plurality of data sets through a first write channel to a hard disk drive. A verification module verifies whether a representative data set of the plurality of data sets is successfully written to the first write channel or not. A mitigation module rewrites the plurality of data sets in response to an unsuccessful write of the representative data set.

Abstract: Provided are a method, system, and article of manufacture for using different algorithms to destage different types of data from cache. A first destaging algorithm is used to destage a first type of data to a storage for a first duration. A second destaging algorithm is used to destage a second type of data to the storage for a second duration.

Abstract: Embodiments of the invention relate to automated system problem diagnosing. An index is created with problem description information of previously diagnosed problems, a diagnosis for each problem, and a solution to each diagnosis. System states, traces and logs are extracted from a source system with a new problem. The problem diagnosis system generates problem description information of the new problem from the system states, traces and logs. Problem description information of the new problem is compared with problem description information in the problem description index. A search score is computed for each document in the problem description index. The search score is a measure of similarity between each document in the index and the description of the new problem. A matching score is assigned to each previously diagnosed problems based on the search score. The matching score is a measure of similarity between the new problem and each previously diagnosed problem.

Abstract: Network latencies are reduced by detecting a metadata access call for filesystem metadata contained in a filesystem node of remotely located filesystem. The metadata corresponding to the metadata access call is fetched when the metadata corresponding to the metadata access call is not contained in a local filesystem cache that has a hierarchical structure corresponding to a hierarchical structure of the remotely located filesystem. Metadata related to the metadata corresponding to the metadata access call from the remotely located filesystem is prefetched when the related metadata is not contained in the local filesystem cache. The metadata related to the metadata corresponding to the access call can be contained in a child node or a parent node of the node containing the metadata corresponding to the access call, or the descendants of such nodes.

Abstract: Embodiments of the invention relate to automated system problem diagnosing. An index is created with problem description information of previously diagnosed problems, a diagnosis for each problem, and a solution to each diagnosis. System states, traces and logs are extracted from a source system with a new problem. The problem diagnosis system generates problem description information of the new problem from the system states, traces and logs. Problem description information of the new problem is compared with problem description information in the problem description index. A search score is computed for each document in the problem description index. The search score is a measure of similarity between each document in the index and the description of the new problem. A matching score is assigned to each previously diagnosed problems based on the search score. The matching score is a measure of similarity between the new problem and each previously diagnosed problem.

Abstract: Provided are a method, system and program for using multiple data structures to manage data in cache. A plurality of data structures each have entries identifying data from a first computer readable medium added to a second computer readable medium. A request is received for data in the first computer readable medium. A determination is made as to whether there is an entry for the requested data in one of the data structures. The requested data is retrieved from the first computer readable medium to store in the second computer readable medium in response to determining that there is no entry for the requested data in one of the data structures. One of the data structures is selected in response to determining that there is no entry for the requested data in one of the data structures and an entry for the retrieved data is added to the selected data structure.

Abstract: A method and system for cache-based dropped write protection in data storage systems are provided. An implementation involves detecting undetected write errors in a storage system, by writing data to a storage medium from a data cache; maintaining a copy of the data in the data cache until said data on the storage medium is validated or said data needs to be evicted from the data cache; and prior to eviction of said data from the data cache, maintaining metadata for said data in a metadata cache until the data written to the storage medium has been validated against the metadata.

Abstract: A self-tuning, low overhead, simple to implement, locally adaptive, novel cache management policy that dynamically and adaptively partitions the cache space amongst sequential and random streams so as to reduce read misses.

Abstract: Provided are a method, system, and article of manufacture for using different algorithms to destage different types of data from cache. A first destaging algorithm is used to destage a first type of data to a storage for a first duration. A second destaging algorithm is used to destage a second type of data to the storage for a second duration.

Abstract: A system and method is disclosed for maintaining, in a Storage Area Network (SAN), the consistency of a local copy of a remote file system sub-tree obtained from a remote source. Directory structure of the remote file system sub-tree is mapped to a remote container attached to the SAN and each remote object of the remote file system sub-tree is represented as a local object component of the remote container. Next, each of the local objects are labeled with attributes associated with the represented remote object, and metadata describing each of the local objects is stored in a metadata server. Also, a consistency policy is associated with each of the local objects in the remote container (wherein the policy defines conditions for checking freshness of said labeled attributes), and the local object components of remote container is updated in accordance with the consistency policy.

Abstract: Provided are a method, system, and article of manufacture for using different algorithms to destage different types of data from cache. A first destaging algorithm is used to destage a first type of data to a storage for a first duration. A second destaging algorithm is used to destage a second type of data to the storage for a second duration.

Abstract: Provided are a method, system, and article of manufacture for managing write requests in cache directed to different storage groups. A determination is made of a high and low thresholds for a plurality of storage groups configured in a storage, wherein the high and low thresholds for one storage group indicate a high and low percentage of a cache that may be used to store write requests to the storage group. A determination is made of a number of tasks to assign to the storage groups based on the determined high and low thresholds for the storage groups, wherein each task assigned to one storage group destages write requests from the cache to the storage group.

Abstract: A self-tuning, low overhead, simple to implements locally adaptive, novel cache management policy that dynamically and adaptively partitions the cache space amongst sequential and random streams so as to reduce read misses.

Abstract: Provided are a method, system, and article of manufacture for adjusting parameters used to prefetch data from storage into cache. Data units are added from a storage to a cache, wherein requested data from the storage is returned from the cache. A degree of prefetch is processed indicating a number of data units to prefetch into the cache. A trigger distance is processed indicating a prefetched trigger data unit in the cache. The number of data units indicated by the degree of prefetch is prefetched in response to processing the trigger data unit. The degree of prefetch and the trigger distance are adjusted based on a rate at which data units are accessed from the cache.

Abstract: Addressed is a system and method for remote data caching and replication by local copy maintenance of remote data within a SAN file system. Distributed Storage Tank (DST), an extension to a SAN file system, provides for transparent SAN client access of local copies by importing, exporting, and storing data using network file access protocols as well as by providing assurance of metadata and file content validity. A Remote Access Agent (RAA) handles protocol implementation and conversion necessary for communication with remote data sources. Controlled by a consistency policy, consistency is maintained by RAA fetching and updating local copies if modifications have occurred to a file since it was first stored as a local copy in local storage. Additionally, RAA returns metadata pertaining to the requested data. A SAN client obtains metadata corresponding to the requested data and utilizes it to directly access locally stored copies of remote data.

Abstract: A method and system for cache-based dropped write protection in data storage systems are provided. An implementation involves detecting undetected write errors in a storage system, by writing data to a storage medium from a data cache; maintaining a copy of the data in the data cache until said data on the storage medium is validated or said data needs to be evicted from the data cache; and prior to eviction of said data from the data cache, maintaining metadata for said data in a metadata cache until the data written to the storage medium has been validated against the metadata.

Abstract: A write cache provides for staging of data units written from a processor for recording in a disk. The order in which destages and validations occur is controlled to make validations more efficient. The data units are arranged in a circular queue according to their respective disk storage addresses. Each data unit is tagged with a state value of 1, 0, or ?1. A destaging pointer is advanced one-by-one to each data unit like the hand of a clock. Each data unit pointed to is evaluated as a destage victim. The first step is to check its state value. A data unit newly brought into the write cache will have its state value reset to 0. It will stay that way until it receives an overwrite x command or the destage pointer clocks around to x. If an overwrite x, the state value is set to 1, in a way, indicating recent use of the data unit and postponing its destaging and eviction. If the destage pointer clocks around to x when the state was 0, then it's time to destage x and the state value is changed to ?1.

Abstract: A method of extending functionality of a data storage facility by adding to the primary storage system new functions using extension function subsystems is disclosed. One example of extending the functionality includes compressing and caching data in a data storage facility to improve storage and access performance of the data storage facility. A primary storage system queries a data storage extension system for availability of data tracks. If the primary storage system does not receive a response or the data tracks from the data storage extension system, it continues caching by fetching data tracks from a disk storage system. The storage extension system manages compression/decompression of data tracks in response to messages from the primary storage system. Data tracks transferred from the data storage extension system to the primary storage system are marked as stale at the data storage extension system and are made available for deletion.

Abstract: A storage system has a storage controller for an array of storage disks, the array being ordered in an sequence of write groups. A write cache is shared by the disks. The storage controller temporarily stores write groups in the write cache, responsive to write groups being written, and lists the write groups in order of their sequence in the array and in circular fashion, so that a lowest is listed next to a highest one of the write groups. The storage controller selects the listed write groups in rotating sequence. Such a write group is destaged from the write cache to the disk responsive to i) the selecting of the write group and ii) a state of a recency indicator for the write group, wherein the recency indicator shows recency of writing to the write group.

Abstract: A self-tuning, low overhead, simple to implement, locally adaptive, novel cache management policy that dynamically and adaptively partitions the cache space amongst sequential and random streams so as to reduce read misses.