International Business Machines Corporation

Jerry Wayne Pence

Cuong Minh Le

James Mitchell Ratliff

Lyn Lequam Ashton

Anthony Steve Pearson

Harvey E Kamionka

Richard Anthony Ripberger

Scott Milton Fry

Glenn Randle Wilcock

Wayne Erwin Rhoten

Thomas William Beglin

Warren B Harding

Vincent K Allen

Robert G Long

Gregory E McBride

David Gregory Van Hise

Stanley Mark Kissinger

Stephen C West

William D McEwen

Lyn Leguam Ashton

Dat M Tran

Jane R Pence

Jane R Bittihoffer

Robert C Buddecke

Cheryl Jean Knapp

A technique for determining an optimal number of tasks for processing requests is provided. It is determined whether there are one or more first requests that have not been processed. A parallelism assessment is performed for simulating the assignment of said first requests to one or more task representations.

Work load assessment heuristic for optimal task parallelism determination

In a data storage system with multiple output media types, each request to store a data object is automatically analyzed to select the optimal output media type. In choosing the output media type best suited to quickly and efficiently complete the storage requests, the storage system considers (1) attributes of the data object itself, such as its size, (2) any perceived urgency required to complete the data storage request, and (3) attributes of the system's storage devices, such as the availability of different output media types, presence of other storage requests queued for storage for each type, level of ongoing access of each storage type by concurrent storage tasks, delays to initiate storage such as mount/demount times, amount of storage space available in different output media types, and the like.

Data storage system with automatic storage request analysis and selection of optimal output media type

In a computing system with non-shareable resources, use-arbitrating processes are executed on behalf of each task seeking or having access to non-shareable resource. The processes compete according to prescribed rules and priority guidelines, the resolution of which determines access to the non-shareable resource. If application of the priority guidelines permits, a use-requesting task can institute takeaway of a resource from a task that is already using the resource.

Computing system arbitrating and selectively providing resource-seeking tasks with takeaway of non-shareable resources

In a data storage system that employs multiple storage drives to access removable data storage media, idle data storage media are analyzed and than selectively demounted by automated equipment to increase storage drive availability and also minimize unnecessary mount/demount operations. Initially, the system establishes a maximum permitted number of concurrently mounted idle storage media, and also establishes a maximum permitted length of time for leaving idle storage media mounted. Next, storage media mounted to the media drives are analyzed for possible demounting. The system determines how many storage media are presently mounted, and each media's mount time. Then, the system identifies suitable demounting candidates (if any) to comply with the established maximums. Namely, the system identifies the media with the greatest idle times whose demounting is necessary to both (1) reduce the number of concurrent mounts down to the maximum permitted number, and (2) demount any storage media with idle times exceeding the maximum permitted length of time..

Multi-drive data storage system with analysis and selected demounting of idle data storage media

A data management system responds to migration requests by automatically invoking a shortcut migration process for suitable candidates. Suitability of candidate data is efficiently evaluated using, among other considerations, the presence or absence of an expedited access indicator for the data which is previously set when the data is recalled from backup storage. In the shortcut migration process, the system automatically reconnects a previously migrated copy of the data object, if available.

Data management system with shortcut migration via efficient automatic reconnection to previously migrated copy

Disclosed is a system for handling recall requests for data maintained in storage devices from a host system. The host system maintains a queue of recall requests to a plurality of storage devices. Priority data is associated with each recall request in the queue. The host system initiates a recall operation for a recall request in the queue to a first storage device mounted in a drive. The host system then determines whether a next recall request to the first storage device has a higher priority than a recall request to a second storage device not mounted in a drive. The recall operation for the next recall request to the first storage device is performed after determining that the next recall request has the higher priority. The first storage device is demounted from the drive after determining that the recall request to the second storage device has the higher priority. The second storage device to the drive is mounted after demounting the first storage device from the drive. The recall operation for the recall request to the second storage device is then performed.

Contention handling for task requests to storage devices within a host system

Disclosed is a system for handling recall requests for data maintained in a storage device accessible to multiple systems. Initially, a storage device is allocated to the first host system to process recall requests in a recall queue including a plurality of recall requests. A second host recall request is initiated with the second host system to recall data from the storage device. The second host system determines whether the storage device is allocated to the first host system. If so, the second host systems stores priority data in a common or shared data structure indicating a priority of the second host recall request after determining that the storage device is allocated to the first host system. The first host system then conditionally releases the storage device before processing all the recall requests needing the subject tape in its queue to make the storage device available if the priority in the common data structure is higher than its own highest priority request. The second host system retries the second host recall request after the first host system releases the storage device. The second host system then determines whether the storage device is available and whether the highest priority second host recall request is greater than or equal to the priority data indicated in the data structure when retrying the second host recall request. The storage device is allocated to the second host system to process the second host recall request after determining that the storage device is available and that the priority of the second host recall request is greater than or equal to the priority data indicated in the data structure.

System using priority data of a host recall request to determine whether to release non-volatile storage with another host before processing further recall requests

A system and method for increasing capacity utilization of non-volatile storage devices within a group of non-volatile storage devices used to store data from at least one attached system are disclosed. A group of data sets is written to a first storage device as part of a write operation such as migration. A plurality of storage devices partially filled with data are designated as substitutes. The write operation to the first storage device is suspended upon receiving a request to read a data set stored in the first storage device, such as occurs in a recall operation. A second storage device is then selected from the plurality of substitute storage devices. The write operation is continued by writing data sets from the group of data sets included in the write operation that were not written to the first storage device to the selected second storage device. The requested data is then read from the first storage device. After data has been read from the first storage device, the first storage device may be designated as a substitute storage device so that the partially filled first storage device may be selected for continuing write operations. Data sets from substitute storage devices may be transferred or merged into a lesser number of storage devices during recycle operations to prevent the number of substitute storage devices from increasing beyond a predetermined limit or goal. Recycling operations in which data sets from different storage devices are transferred or merged may be performed by building a first queue including a list of filled tapes ordered according to the least amount of valid data and a second queue including all unassociated partially filled storage devices ordered by the amount of available storage space, and merging. The non-volatile storage devices may include tapes or tape libraries.

Storage management system and method for increasing capacity utilization of nonvolatile storage devices using partially filled substitute storage devices for continuing write operations

A method for creating a duplicate copy of a tape in which a first tape having a first data set name and a second tape having a second data set name are allocated. Data is written to the first and second tapes so that block for block, the data is located at the same position on each of the tapes. After data is written to one of the tapes, a check is made to verify that the data was written correctly. If an error is detected in writing the second tape, an error flag is set that indicates a copy of the first tape needs to be made. At various stages of the process, checks are made to determine if error flag is on. If the error flag is detected, writing the second tape is suspended.

Tape duplexing with unique identity and error recovery

A data processing system includes a data storage subsystem containing a plurality of data storage devices for reading and writing data on a plurality of data storage volumes. The data processing system is controlled by software to perform a method for recycling the data storage volumes containing a percentage of still valid data and a percentage of invalid data by transferring the still valid data on a plurality of input data storage volumes to one or more output data storage volumes. In accordance with the recycling method, the data processing system assigns a selected number of the data storage devices as input devices and a selected number of the data storage devices as output devices in a predetermined input/output ratio of the form m:k, where m is the number of input devices and k is the number of output devices. The system then commences transferring still valid data from input volumes mounted on the input devices to output volumes mounted on the output devices. As each volume is transferred, the system monitors the data transfer efficiency from the input devices to the output devices and adjusts the input/output ratio based on the measured data transfer efficiency.

Dynamic reconfiguration of data storage devices to balance recycle

A system for recovering multi-volume data sets that are stored in one or more volumes that have failed with a substantial level of automation and flexibility. Data can be recovered from backup storage when multiple volumes fail, as in a 'catastrophic' data loss. For each volume, all data sets partially or completely stored on the selected volume prior to a failure of that volume are identified. Each single-volume data set stored on the selected volume prior to the failure is restored from backup storage. Upon identifying a multi-volume data set whose beginning segment was stored on the selected volume, the entire data set is restored. Data can also be recovered from backup storage when a particular volume fails, such as after a 'head crash.' All data sets partially or completely stored on the selected volume prior to a failure of that volume are identified. Each single volume data set stored on the selected volume prior to the failure is recovered from backup storage. For each multi-volume data set having a segment stored on the selected volume prior to the failure, a predetermined message is issued to a human operator. Alternatively, multi-volume data sets are recovered if consistent. Otherwise, if valid data has been lost, a warning message is issued.

Recovering multi-volume data sets during volume recovery

A procedure for the optimal processing of variable-cost actions such as encountered in the storage reclamation procedures for a multivolume data library. The procedure introduces a temporary processing queue to minimize idle processing capacity during the scanning and sorting of a large plurality of variable-cost actions such as the recycling of a plurality of data storage volumes each having a variable recycle processing cost related to the action of valid data remaining on the volume. Volumes (actions) are selected for the immediate queue according to a dynamically-adjusted threshold test for the processing cost. This processing cost threshold is dynamically adjusted to optimize the immediate queue in relation to the available processing capacity. After scanning and sorting all volumes according to recycle processing cost, the temporary (immediate) queue is updated to a final recycle processing queue by appending a sorted deferred queue to the remainder of the immediate queue. The procedure of this invention minimizes idle processing capacity during the queue-building interval, thereby optimizing the number of recovered data storage volumes released in a given time interval.

System for performing action by sorting actions into immediate and

An adaptive data transfer channel providing means for a data management access method (AM) to define the channel subsystem data block transfer size and to transfer an extended data block (EDB) by a single channel transfer command to avoid repeated channel command word (CCW) command decode and status presentation operations. The adaptive scheme of this invention is transparent to the user and downwardly compatible with existing data record storage formats because it is independent of the user application program. The host software in the central processing complex (CPC) tests the peripheral data storage device (PDSD) to ensure compatibility with the EDB CCWs before selecting the channel program (CP) to be used for data block transfer in the subchannel. In the EDB format, the PDSD microcode permits the accumulation of logical data blocks (LDBs) from storage to form a single large EDB before transfer to the CPC responsive to a single transfer command. Conversely, the CPC can transfer a single EDB to the PDSD where it is parsed to form data records in an existing data record storage format, thus ensuring complete downward compatibility with existing data record storage formats.

Extension of data block capability in a data transfer channel

Adaptive data transfer channel employing extended data block capability

A method for efficiently utilizing data recording media in a data processing system performing data compression beneath the level of the host processor is disclosed. To improve the ability of a recording media to be copied without increasing host processor overhead, the control unit which sees the compressed data is checked only upon recording a predetermined amount of uncompressed data. At such time, a compression ratio is calculated for the current data set and is used to monitor the recording of the remaining data of the current data set in compressed form. When a predetermined amount of compressed data is estimated to be recorded, the predetermined amount being the minimum storage capacity of a recording media, recording begins on a new recording media. Recording media spanning is reduced by checking counters in the storage device control unit only upon completion of recording an entire data set, and then using the uncompressed size of the next data set to be recorded to determine whether or not to continue recording on the same or a new cartridge.

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Tucson, AZ, United States of America

Jerry Wayne Pence