Abstract: Described are techniques for storing first data to a logical data in accordance with a static policy to service reads using data stored in a first storage area. The logical device has its data stored on a first physical device that is mirrored on a second physical device. Each of the first and second physical devices include a first storage area and a second storage area. The first storage areas provide better performance than the second storage areas. The first data is stored at a first location in one of the first storage areas of one of the physical devices and at a second location in one of the second storage areas at the other of the first and the second physical devices. An operation to read the first data is serviced by accessing the first data stored in the first area of the one physical device.

Abstract: Measuring access rates of a computer memory include subdividing the memory into subsections, monitoring access rates for each of the subsections, in response to a subsection having a relatively high access rate, subdividing the subsection into multiple subsections that are separately monitored, and, in response to at least two adjacent subsections having a relatively low access rate, merging the at least two subsections into a single subsection. Monitoring access rates may include monitoring at least one of the following operational parameters: number of data accesses, number of cache accesses, number of cache misses, number of read accesses, number of write accesses, and ratio of read accesses to write accesses. Two or more operational parameters may be used and the operational parameters may be weighted.

Abstract: This invention is a system and method for configuring a data storage system based on workload, response time, or utilization requirements. The method includes the steps of receiving workload, utilization or response time data, analyzing the respective received data, determining a configuration for a data storage system which may be available in report form to a user.

Abstract: Described are techniques for determining a cache slot. A set of criteria for each of a plurality of families is received. A received data operation associated with a first of said plurality of families is obtained. It is determined, in accordance with the criteria associated with the received data operation, whether to allocate a cache slot in the cache for the received data operation. The criteria for the first family includes a minimum value and a maximum value used in determining a cache partition size range for the first family. The maximum value is used in determining a maximum cache partition size allowable for the first family.

Abstract: Described is a process and device for accessing data stored in multiple logical volumes. The data are replicated on first and second storage elements, such as the redundant hard disk drives of a disk mirror. The multiple logical volumes are divisible into a first logical volume and a second logical volume. All read requests targeting the first logical volume are directed to one of the first and second storage elements. Read requests targeting the second logical volume are asymmetrically interleaved between the first and second storage elements. An asymmetric interleave ratio is determined and implemented that substantially balances the read requests to the multiple logical volumes between the first and second storage elements.

Abstract: Destaging activities in a data storage system are controlled by providing a write pending list of elements, where each element is defined to store information related to a cache memory data element for which a write to storage is pending, and maintaining the write pending list so that destaging of a data element can be based on the maturity of the pending write.

Abstract: A method for implementing the invention is carried out in a data-storage system having a data storage unit that includes at least two constituent data storage elements. Each of the constituent data storage elements is either in a first state or a second state. The method includes providing a data structure having an entry corresponding to the data storage unit. The entry includes status information indicating whether at least one constituent data storage element of the data storage unit is in the first state. These entries are updated as necessary following any changes in state of the constituent data storage element. Scanning the data storage units instead of the data storage elements provides a more efficient way to locate data storage elements in the first state, particularly where such data storage elements are rare.

Abstract: This invention is a system and method for simulating performance of one or more data storage systems. This invention may be used in many useful ways including for configuring or modeling a data storage environment, problem isolation, and general design.

Abstract: A mixed queue method for managing storage requests directed includes a low-priority request queue on which all low-priority requests are placed and where they are subject to throughput optimization by re-ordering. When a high-priority request limit has not been reached, high-priority requests are placed on a high-priority request queue where they are executed in a pre-emptive manner with respect to the queued low-priority requests, thus experiencing reduced access time. When the high-priority request limit has been reached, the high-priority requests are placed on the low-priority request queue, such that the high-priority requests are included in the throughput optimization along with the low-priority requests on the request queue. Starvation of the low-priority requests is avoided, and the overall throughput of the disk drive is maintained at a relatively high level.

Abstract: Destaging activities in a data storage system are controlled by providing a write pending list of elements, where each element is defined to store information related to a cache memory data element for which a write to storage is pending, and maintaining the write pending list so that destaging of a data element can be based on the maturity of the pending write.

Abstract: Techniques and criteria are used in connection with promoting a slot within a cache in the form of a replacement queue. A cache slot may be promoted based on an inequality that considers the following criteria: probability of losing a cache hit, gaining a cache hit, and the price or cost associated with promoting a slot. The foregoing criteria may be used in accordance with a predetermined promotion policy when the replacement queue is in a locked state and an unlocked state, or only when the replacement queue is in a locked state. Different costs may be associated with the state of the replacement queue as locked or unlocked as the replacement queue may be locked in connection with operations that are performed on the replacement queue. The cost associated with a locked replacement queue may be different than the cost associated with an unlocked replacement queue. Different thresholds and values associated with the foregoing criteria may be specified as dynamic system parameters.