Abstract: A method for improving cache hit ratios for selected volumes when using synchronous I/O is disclosed. In one embodiment, such a method includes establishing, in cache, a first set of non-favored storage elements from non-favored storage areas. The method further establishes, in the cache, a second set of favored storage elements from favored storage areas. The method calculates a life expectancy for the non-favored storage elements to reside in the cache prior to eviction. The method further executes an eviction policy for the cache wherein the favored storage elements are maintained in the cache for longer than the life expectancy of the non-favored storage elements. A corresponding system and computer program product are also disclosed.

Abstract: A method for improving cache hit ratios for selected volumes within a storage system includes monitoring I/O to multiple volumes residing on a storage system. The method determines, from the I/O, which particular volumes of the multiple volumes would benefit the most if provided favored status in cache of the storage system, where the favored status provides increased residency time in the cache compared to volumes not having the favored status. The method determines, from the I/O, an amount by which the increased residency time should exceed a residency time of volumes not having the favored status. The method generates an indicator that is representative of the amount and transmits this indicator to the storage system. The storage system, in turn, provides increased residency time to the particular volumes in accordance with the favored status and indicator. A corresponding system and computer program product are also disclosed.

Abstract: A method for improving cache hit ratios for selected storage elements within a storage system is disclosed. In one embodiment, such a method includes storing, in a cache of a storage system, non-favored storage elements and favored storage elements. The favored storage elements are retained in the cache longer than the non-favored storage elements. The method maintains a first LRU list containing entries associated with non-favored storage elements and designating an order in which the non-favored storage elements are evicted from the cache, and a second LRU list containing entries associated with favored storage elements and designating an order in which the favored storage elements are evicted from the cache. The method moves entries between the first LRU list and the second LRU list as favored storage elements are changed to non-favored storage elements and vice versa. A corresponding system and computer program product are also disclosed.

Abstract: A method for improving cache hit ratios for selected volumes within a storage system is disclosed. In one embodiment, such a method includes monitoring I/O to multiple volumes residing on a storage system. The storage system includes a cache to store data associated with the volumes. The method determines, from the I/O, which particular volumes of the multiple volumes would benefit the most if provided favored status in the cache. The favored status provides increased residency time in the cache to the particular volumes compared to volumes not having the favored status. The method generates a list of the particular volumes and transmits the list to the storage system. The storage system, in turn, provides increased residency time to the particular volumes in accordance with their favored status. A corresponding system and computer program product are also disclosed.

Abstract: A computational device determines whether one or more tasks are waiting for accessing a cache for more than a predetermined amount of time while least recently used (LRU) based replacement of tracks are being performed for the cache via demotion of tracks from a LRU list of tracks corresponding to the cache. In response to determining that one or more tasks are waiting for accessing the cache for more than the predetermined amount of time, in addition to continuing to demote tracks from the LRU list, a plurality of deadlock prevention demotion tasks demote tracks from the cache.

Abstract: A dual-server based storage system maintains a first cache and a first non-volatile storage (NVS) in a first server, and a second cache and a second NVS in a second server, where data in the first cache is also written in the second NVS and data in the second cache is also written in the first NVS. In response to a failure of the first server, a determination is made as to whether space exists in the second NVS to accommodate the data stored in the second cache. In response to determining that space exists in the second NVS to accommodate the data stored in the second cache, the data is transferred from the second cache to the second NVS.

Abstract: Provided are a computer program product, system, and method for managing processor threads of a plurality of processors. In one embodiment, a parameter of performance of the computing system is measured, and the configurations of one or more processor nodes are dynamically adjusted as a function of the measured parameter of performance. In this manner, the number of processor threads being concurrently executed by the plurality of processor nodes of the computing system may be dynamically adjusted in real time as the system operates to improve the performance of the system as it operates under various operating conditions. It is appreciated that systems employing processor thread management in accordance with the present description may provide other features in addition to or instead of those described herein, depending upon the particular application.

Abstract: Provided are a computer program product, system, and method for receiving, at a secondary storage controller, information on modified data from a primary storage controller to use to calculate parity data. The secondary storage controller receives from the primary storage controller difference data calculated from modified data and a pre-modified version of the modified data for a primary group of tracks at the primary storage and one of the modified data and new primary parity data calculated at the primary storage controller from the modified data and the difference data. The secondary storage controller uses the difference data and one of the modified data and the new primary parity data to write new secondary parity data and the modified data to a secondary group of tracks at the secondary storage.

Abstract: Provided are a computer program product, system, and method for updating a track format table used to provide track format codes for cache control blocks with more frequently accessed track format metadata. A track format table associates track format codes with track format metadata. Each instance of the track format metadata indicates a layout of data in a track. Cache control blocks for tracks in the cache include track format codes associated with the track format metadata of the tracks in the cache. Track format access information indicating accesses of track format metadata not included in the track format table. Track format metadata, indicated in the track format access information that is not in the track format table, is added to the track format table to associate with a track format code based on a number of accesses of the track format metadata indicated in the track format access information.

Abstract: In one embodiment, virtual storage drives are allocated to RAID arrays so that no two virtual storage drives of a RAID array are mapped to the same physical storage drive. In another aspect, error handling routines are limited to virtual storage drives impacted by an error in a physical storage drive so that virtual storage drives of the physical storage drive not impacted by the error are bypassed. In yet another aspect, cache operations to a target virtual storage drive may be throttled as a function of both a limit imposed on cache operations directed to the RAID array to which the virtual storage drive is allocated, and a separate limit on cache operations directed to a group of virtual storage drives which are mapped to the same physical storage drive as the target virtual storage drive. Other features and aspects may be realized, depending upon the particular application.

Abstract: Provided are a computer program product, system, and method for using a machine learning module to select one of multiple cache eviction algorithms to use to evict a track from the cache. A first cache eviction algorithm determines tracks to evict from the cache. A second cache eviction algorithm determines tracks to evict from the cache, wherein the first and second cache eviction algorithms use different eviction schemes. At least one machine learning module is executed to produce output indicating one of the first cache eviction algorithm and the second cache eviction algorithm to use to select a track to evict from the cache. A track is evicted that is selected by one of the first and second cache eviction algorithms indicated in the output from the at least one machine learning module.

Abstract: Provided are a computer program product, system, and method for destaging metadata tracks from cache A counter for a metadata track is updated in response to modifying the metadata track in the cache, wherein there are counters for metadata tracks in the cache. The metadata track is destaged from the cache in response to the counter for the metadata track being less than a threshold value. The counter for the metadata track is decremented based on a number of modified metadata tracks in the cache.

Abstract: Provided are a computer program product, system, and method for performing workload balancing of tracks in storage areas assigned to processing units. For each processing unit, there is an assignment of a storage area of tracks in the storage to the processing unit, at least one queue having I/O requests to the storage area, and queue usage information indicating a quantity related to the I/O requests in the at least one queue. A determination is made from the queue usage information whether to perform workload balancing for a source processing unit having at least one source queue. A target processing unit is selected in response to determining to perform the workload balancing for the source processing unit. Tracks in a source storage area assigned to the source processing unit are moved to a target storage area assigned to the target processing unit.

Abstract: A method for increasing effective storage capacity in a heterogeneous storage array is disclosed. In one embodiment, such a method determines a number of smaller-capacity storage drives and a number of larger-capacity storage drives in a storage array. The method further determines which RAID arrays in the storage array may be composed exclusively of the larger-capacity storage drives. Using this information, the method establishes a first set of RAID arrays in the storage array that will be composed exclusively of the larger-capacity storage drives and a second set of RAID arrays that may contain the smaller-capacity storage drives. The method then initiates a process to swap the smaller-capacity storage drives in the first set with the larger-capacity storage drives in the second set until the first set of RAID arrays is composed exclusively of the larger-capacity storage drives. A corresponding system and computer program product are also disclosed.

Abstract: Provided are a method, system, and computer program product in which a storage controller receives a first write command with a first token over a first interface from a host computational device. In response to a failure of the first write command in the storage controller, the storage controller retains selected resources for reuse for a retry of the first write command, wherein the retry of the first write command is expected from the host computational device over a second interface that is a slower communication link than the first interface. In response to receiving, by the storage controller, a second write command with a second token over the second interface, wherein the second token is identical to the first token, the storage controller determines that the second write command is a retry of the first write command and reuses the retained selected resources for executing the second write command.

Abstract: A host computational device transmits a first write command with a first token over a first interface to a storage controller. In response to receiving an indication by the host computational device that the first write command has failed in the storage controller, the host computational device transmits a second write command with a second token over a second interface to the storage controller, wherein the second write command is a retry of the first write command that failed, wherein the second token is identical to the first token, and wherein the second interface is a slower communication link than the first interface.

Abstract: Provided are techniques for synchronously performing commit records operations. A local copy of a commit records message is built for a Non-Volatile Storage (NVS) track, with a valid indicator set to indicate that this commit records message is valid and has not been processed yet. A Direct Memory Access (DMA) chain is executed to transfer customer data from a host to real segments and alternate segments of a track buffer and to transfer the local copy of the commit records message to a mail message structure of a mail message array. At DMA completion, an NVS manager is synchronously called to perform a commit records operation with the commit records message in the mail message structure. In response to the commit records operation completing, there is an indication that a new write DMA is allowed to proceed for the NVS track.

Abstract: Provided area computer program product, system, and method for maintaining track format metadata for target tracks in a target storage in a copy relationship with source tracks in a source storage. Upon receiving a request to a requested target track in the target storage, the source track for the requested target track is staged from the source storage to a cache to be used as the requested target track in response to determining that the copy relationship information indicates that a source track needs to be copied to the requested target track. A determination is made of track format metadata for the requested target track, comprising the staged source track, indicating a format and layout of data in the requested target track and a track format code identifying the track format metadata. The track format code is included in a cache control block for the requested target track.

Abstract: A method for reducing I/O performance impacts associated with a data commit operation is disclosed. In one embodiment, such a method includes periodically performing a data commit operation wherein modified data is destaged from cache to persistent storage drives. Upon performing a particular instance of the data commit operation, the method determines whether modified data in the cache is a metadata track. In the event the modified data is a metadata track, the method attempts to acquire an exclusive lock on the metadata track. In the event the exclusive lock cannot be acquired, the method skips over the metadata track without destaging the metadata track for the particular instance of the data commit operation. A corresponding system and computer program product are also disclosed.

Abstract: Provided are a computer program product, system, and method for determining when to send message to a computing node to process items using a machine learning module. A send message threshold indicates a send message parameter value for a send message parameter indicating when to send a message to the computing node with at least one requested item to process. Information related to sending of messages to the computing node to process requested items is provided to a machine learning module to produce a new send message parameter value for the send message parameter indicating when to send the message, which is set to the send message parameter value. A message is sent to the computing node to process at least one item in response to the current value satisfying the condition with respect to the send message parameter value.