Abstract: Power consumption can be reduced by preventing a memory image from being destaged to a nonvolatile memory device. For example, a system can determine, subsequent to a computing device being in a first power mode and having a memory image stored in a first nonvolatile memory device that performs a caching function, that the computing device is in a second power mode that is a higher power mode than the first power mode. The system can, in response to determining that the computing device is in the second power mode, generate a first command to store the memory image in a volatile memory device and prevent the memory image from being stored in a second nonvolatile memory device. The system can, in response to generating the first command, store the memory image in the volatile memory device.

Abstract: A storage system may assign a different encryption key to each logical storage unit (LSU) of a storage system. For each LSU, the encryption key of the LSU may be shared only with host systems authorized to access data of the LSU. In response to a read request for a data portion received from a host application executing on the host system, encryption metadata for the data portion may be accessed. If it is determined from the encryption metadata that the data portion is encrypted, the data encryption metadata for the data portion may be further analyzed to determine the encryption key for the data portion. The data may be retrieved from the storage system, for example, by performance of a direct read operation. The retrieved data may be decrypted, and the decrypted data may be returned to the requesting application.

Abstract: Techniques for processing I/O operations may include: issuing, by a process of an application on a host, an I/O operation; determining, by a driver on the host, that the I/O operation is a read operation directed to a logical device used as a log to log writes performed by the application, wherein the read operation reads first data stored at one or more logical addresses of the logical device; storing, by the driver, an I/O flag in the I/O operation, wherein the I/O flag has a first flag value denoting an expected read frequency associated with the read operation; sending the I/O operation from the host to the data storage system; and performing first processing of the I/O operation on the data storage system, wherein said first processing includes using the first flag value in connection with caching the first data in a cache of the data storage system.

Abstract: A first host device establishes connectivity to a logical storage device of a storage system. The first host device obtains from the storage system host connectivity information identifying at least a second host device that has also established connectivity to the logical storage device, caches one or more extents of the logical storage device in a memory of the first host device, and maintains local cache metadata in the first host device regarding the one or more extents of the logical storage device cached in the memory of the first host device. In conjunction with processing of a write operation of the first host device involving at least one of the one or more cached extents of the logical storage device, the first host device invalidates corresponding entries in the local cache metadata of the first host device and in local cache metadata maintained in the second host device.

Abstract: Data compression is performed on a storage system for which one or more host systems have direct access to data on the storage system. The storage system may compress the data for one or more logical storage units (LSUs) having data stored thereon, and may update compression metadata associated with the LSUs and/or the data portions thereof to reflect that the data is compressed. In response to a read request for a data portion received from a host application executing on the host system, compression metadata for the data portion may be accessed. If it is determined from the compression metadata that the data portion is compressed, the data compression metadata for the data portion may be further analyzed to determine how to decompress the data portion. The data portion may be retrieved and decompressed, and the decompressed data may be returned to the requesting application.

Abstract: In response to receiving a read metadata request from the host system for a data portion, the storage system may determine a status and location of the data portion, including determining whether the data portion is in a cache of the storage system. If the data portion is in the cache, the storage system may send a response that includes the data portion itself along with the status and location of the data portion. If the data portion is not in the cache, the storage system may send a response to the read metadata request that includes the status and location of the data portion, but not the data portion itself. The host system may be configured to determine whether the data portion has been returned with the metadata response, and if so, refrain from sending a separate data request, for example, to retrieve the data portion from cache.

Abstract: Writes to one or more physical storage devices may be blocked after a certain storage consumption threshold (WBT) for each physical storage device. A WBT for certain designated physical storage devices may be applied in addition to, or as an alternative to, determining and applying a user-defined background task mode threshold (UBTT) for certain designated physical storage devices. In some embodiments, the WBT and UBTT for a physical storage device designated for spontaneous de-staging may be a same threshold value. Write blocking management may include, for each designated physical storage device, blocking any writes to the designated physical storage device after a WBT for the designated physical storage device has been reached, and restoring (e.g., unblocking) writes to the designated physical storage device after storage consumption on the physical storage device has been reduced to a storage consumption threshold (WRT) lower than the WBT.

Abstract: An apparatus comprises a host device configured to communicate over a network with source and target storage systems. The host device, in conjunction with migration of a logical storage device from the source storage system to the target storage system, is further configured to obtain from the target storage system watermark information characterizing progress of the migration of the logical storage device from the source storage system to the target storage system, and to determine whether a given input-output operation is to be sent to the source storage system or the target storage system based at least in part on the watermark information obtained from the target storage system. The watermark information illustratively identifies a particular logical address in the logical storage device, up to and including for which corresponding data has already been copied from the source storage system to the target storage system in conjunction with the migration.

Abstract: An apparatus comprises a host device configured to communicate over a network with source and target storage systems. The host device, in conjunction with migration of a logical storage device from the source storage system to the target storage system, is further configured to obtain from the target storage system watermark information characterizing progress of the migration of the logical storage device from the source storage system to the target storage system, and to determine whether a given input-output operation is to be sent to the source storage system or the target storage system based at least in part on the watermark information obtained from the target storage system. The watermark information illustratively identifies a particular logical address in the logical storage device, up to and including for which corresponding data has already been copied from the source storage system to the target storage system in conjunction with the migration.

Abstract: A distributed cache is managed. In some embodiments, only a subset of a plurality of processing nodes may be designated as cache managers that manage the cache access history of a logical area, including having an exclusive right to control the eviction of data from cache objects of the logical area. In such embodiments, all of the processing nodes may collect cache access information, and communicate the cache access information to the cache managers. Some of the processing nodes that are not cache managers may collect cache access information from a plurality of the other non-cache managers. Each such processing node may combine this communicated cache access information with the cache access information of the processing node itself, sort the combined information per cache manager, and send the resulting sorted cache access information to the respective cache managers. The processing nodes may be arranged in a cache management hierarchy.

Abstract: A first host device establishes connectivity to a logical storage device of a storage system. The first host device obtains from the storage system host connectivity information identifying at least a second host device that has also established connectivity to the logical storage device, caches one or more extents of the logical storage device in a memory of the first host device, and maintains local cache metadata in the first host device regarding the one or more extents of the logical storage device cached in the memory of the first host device. In conjunction with processing of a write operation of the first host device involving at least one of the one or more cached extents of the logical storage device, the first host device invalidates corresponding entries in the local cache metadata of the first host device and in local cache metadata maintained in the second host device.

Abstract: In response to receiving a read metadata request from the host system for a data portion, the storage system may determine a status and location of the data portion, including determining whether the data portion is in a cache of the storage system. If the data portion is in the cache, the storage system may send a response that includes the data portion itself along with the status and location of the data portion. If the data portion is not in the cache, the storage system may send a response to the read metadata request that includes the status and location of the data portion, but not the data portion itself. The host system may be configured to determine whether the data portion has been returned with the metadata response, and if so, refrain from sending a separate data request, for example, to retrieve the data portion from cache.

Abstract: A storage system may assign a different encryption key to each logical storage unit (LSU) of a storage system. For each LSU, the encryption key of the LSU may be shared only with host systems authorized to access data of the LSU. In response to a read request for a data portion received from a host application executing on the host system, encryption metadata for the data portion may be accessed. If it is determined from the encryption metadata that the data portion is encrypted, the data encryption metadata for the data portion may be further analyzed to determine the encryption key for the data portion. The data may be retrieved from the storage system, for example, by performance of a direct read operation. The retrieved data may be decrypted, and the decrypted data may be returned to the requesting application.

Abstract: Data compression is performed on a storage system for which one or more host systems have direct access to data on the storage system. The storage system may compress the data for one or more logical storage units (LSUs) having data stored thereon, and may update compression metadata associated with the LSUs and/or the data portions thereof to reflect that the data is compressed. In response to a read request for a data portion received from a host application executing on the host system, compression metadata for the data portion may be accessed. If it is determined from the compression metadata that the data portion is compressed, the data compression metadata for the data portion may be further analyzed to determine how to decompress the data portion. The data portion may be retrieved and decompressed, and the decompressed data may be returned to the requesting application.

Abstract: Techniques for processing I/O operations may include: issuing, by a process of an application on a host, an I/O operation; determining, by a driver on the host, that the I/O operation is a read operation directed to a logical device used as a log to log writes performed by the application, wherein the read operation reads first data stored at one or more logical addresses of the logical device; storing, by the driver, an I/O flag in the I/O operation, wherein the I/O flag has a first flag value denoting an expected read frequency associated with the read operation; sending the I/O operation from the host to the data storage system; and performing first processing of the I/O operation on the data storage system, wherein said first processing includes using the first flag value in connection with caching the first data in a cache of the data storage system.

Abstract: A distributed cache is managed. In some embodiments, only a subset of a plurality of processing nodes may be designated as cache managers that manage the cache access history of a logical area, including having an exclusive right to control the eviction of data from cache objects of the logical area. In such embodiments, all of the processing nodes may collect cache access information, and communicate the cache access information to the cache managers. Some of the processing nodes that are not cache managers may collect cache access information from a plurality of the other non-cache managers. Each such processing node may combine this communicated cache access information with the cache access information of the processing node itself, sort the combined information per cache manager, and send the resulting sorted cache access information to the respective cache managers. The processing nodes may be arranged in a cache management hierarchy.

Abstract: In a computer network in which a data storage array maintains data for at least one host computer, the host computer provides sequential access hints to the storage array. A monitoring program monitors a host application running on the host computer to detect generation of data that is likely to be sequentially accessed by the host application along with associated data. When the host application writes such data to a thinly provisioned logical production volume the monitoring program prompts a multipath IO driver to generate the sequential access hint. In response to the hint the storage array allocates a plurality of sequential storage spaces on a hard disk drive for the data and the associated data. The allocated storage locations on the hard disk drive are written in a spatial sequence that matches the spatial sequence in which the storage locations on the production volume are written.

Abstract: Writes to one or more physical storage devices may be blocked after a certain storage consumption threshold (WBT) for each physical storage device. A WBT for certain designated physical storage devices may be applied in addition to, or as an alternative to, determining and applying a user-defined background task mode threshold (UBTT) for certain designated physical storage devices. In some embodiments, the WBT and UBTT for a physical storage device designated for spontaneous de-staging may be a same threshold value. Write blocking management may include, for each designated physical storage device, blocking any writes to the designated physical storage device after a WBT for the designated physical storage device has been reached, and restoring (e.g., unblocking) writes to the designated physical storage device after storage consumption on the physical storage device has been reduced to a storage consumption threshold (WRT) lower than the WBT.

Abstract: Described are data movements techniques may include: receiving a plurality of write quotas for a plurality of physical media types; determining a first physical storage device of a first physical media type that is over utilized with respect to a write quota; selecting a first data portion of the first physical storage device for data movement; determining a target device that is not over utilized with respect to a write quota; determining an expected total write I/O workload of the target device after hypothetically moving the first data portion thereto; determining whether the expected total write I/O workload exceeds a write quota of the target device; and responsive to determining the total write I/O workload does not exceed the write quota for the target device, moving the first data portion to the target storage device.

Abstract: Non-volatile cache in a host computer provides a storage tier in a system that includes at least one other tier of storage in a storage array. Selected data of a host device that represents a storage array production volume is stored in non-volatile cache. An MPIO driver in the host computer accesses the non-volatile cache or the storage array in response to an IO from a host application to the host device. A tiering engine in either the host computer or the storage array uses data access statistics to calculate which data should be promoted or demoted to non-volatile cache. Data access statistics indicative of access to non-volatile cache may be provided to the storage array by the host computer. Data changes may be aggregated by the host computer and asynchronously destaged to the storage array. Data changes or dirty data discard messages may be exchanged by peer host computer synchronously with a write operation.