The disclosure includes a computer-implemented method for providing fast data access after a drive failure, a computer program product, and a RAID controller. One embodiment may comprise identifying a RAID array, the RAID array comprising a plurality of storage volumes, identifying an unused block of a provisioned volume in the RAID array, and copying a redundant copy of high value host writes to the unused block. The copying may comprise, for primary strips in the RAID array, creating one or more secondary strips mirroring the primary strips such that each of pair of primary-secondary strips reside on different storage volumes from each other.

The disclosure includes a computer-implemented method for providing fast data access after a drive failure, a computer program product, and a RAID controller. One embodiment may comprise identifying a RAID array, the RAID array comprising a plurality of storage volumes, identifying an unused block of a provisioned volume in the RAID array, and copying a redundant copy of high value host writes to the unused block. The copying may comprise, for primary strips in the RAID array, creating one or more secondary strips mirroring the primary strips such that each of pair of primary-secondary strips reside on different storage volumes from each other.

Managing connectivity to synchronously replicated storage systems, including: identifying a plurality of storage systems across which a dataset is synchronously replicated; identifying a host that can issue I/O operations directed to the dataset; identifying a plurality of data communications paths between the host and the plurality of storage systems across which a dataset is synchronously replicated; identifying, from amongst the plurality of data communications paths between the host and the plurality of storage systems across which a dataset is synchronously replicated, one or more optimal paths; and issuing, to the host, an identification of the one or more optimal paths.

A storage cluster includes a plurality of storage nodes. Each of the plurality of storage nodes includes nonvolatile solid-state memory and each of the plurality of storage nodes is configured to cooperate with others of the plurality of storage nodes having differing storage capacities in applying erasure coding. The plurality of storage nodes are configured to distribute the user data and metadata throughout the plurality of storage nodes.

Synchronizing snapshots between storage systems, including: receiving, from a source storage system, an identification of a snapshot to be replicated to a destination storage system, wherein the source storage system and the destination storage system are of different types; identifying, from hint information stored on the destination storage system, a most recent version of the snapshot that is stored on the destination storage system; issuing, to the source storage system, a request for an identification of the differences between the snapshot to be replicated to the destination storage system and the most recent version of the snapshot that is stored on the destination storage system; receiving, from the source storage system, the identification of the differences; and issuing a request to transfer, from the source storage system to the destination storage system, data associated with the differences.

Systems for rapidly transferring and, as needed, recovering large data sets and methods for making and using the same. In various embodiments, the system advantageously can allow data to be transferred in larger sizes, wherein data may be easily recovered from multiple regions and wherein latency is no longer an issue, among other things.

In one aspect of metadata track entry sorting in accordance with the present description, recovery logic sorts a list of metadata entries as a function of a source data track identification of each metadata entry to provide a second, sorted list of metadata entries, and generates a recovery volume which includes data tracks which are a function of one or more data target tracks identified by the sorted list of metadata entries. Because the metadata entry contents of the sorted list have been sorted as a function of source track identification number, the particular time version of a particular source track may be identified more quickly and more efficiently. As a result, recovery from data loss may be achieved more quickly and more efficiently thereby providing a significant improvement in computer technology. Other features and aspects may be realized, depending upon the particular application.

In an embodiment, a computer stores source files and source clone files in a source filesystem. The source clone files are shallow copies of the source files, which initially share the same data blocks as the source files. A source file or a source clone file may eventually be modified, where some of the shared blocks are replaced by modified blocks. In a first phase, all data blocks of all source files that are not clones are replicated to a standby filesystem. A second phase compares each clone file on the source filesystem with its base file to detect a set of differed blocks. The second phase copies the differed blocks into the standby filesystem and, in the standby filesystem, applies the differed blocks to a corresponding clone file. Efficiency of keeping the standby filesystem synchronized with the source filesystem is improved by transferring, from the source filesystem to the standby filesystem, only one copy of only data blocks that are modified

Ensuring resiliency to storage device failures in a storage system, including: determining a number of storage device failures within a particular write group that are to be tolerated by the storage system; for a plurality of datasets stored within the storage system, writing each dataset to at least a predetermined number of storage devices within the particular write group, wherein the predetermined number of storage devices is greater than the number of storage device failures within the particular write group that are to be tolerated by the storage system; and responsive to recovering from a system interruption: determining a number of readable storage devices that contain a copy of the dataset; and if the number of readable storage devices that contain a copy of the dataset is not greater than the number of failures that are to be tolerated, writing the dataset to one or more additional storage devices.

Resilient mediation between storage systems replicating a dataset, including: receiving, by a mediation service from one or more storage systems that synchronously replicate a dataset, a request to resolve which storage system continues to service a dataset after the request; and sending, from the mediation service to at least one of the storage systems, a positive mediation result, wherein: the storage systems that received the positive mediation result continue to process data storage requests directed to the dataset, and the storage systems that did not receive a positive mediation result from the mediation service do not continue to process data storage requests directed to the dataset.