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.

A method for improving reliability of a storage system and a related apparatus, where the storage system includes a first control device and a second control device. The method includes receiving, by a target controller, a write request, where the write request includes to-be-written data, and the target controller belongs to the first control device; writing, by the target controller, the to-be-written data into a memory of the target controller; and writing, by the target controller, the to-be-written data into a memory of a mirror controller of the target controller, where at least one mirror controller belongs to the second control device.

One or more techniques and/or computing devices are provided for cross-platform replication. For example, a replication relationship may be established between a first storage endpoint and a second storage endpoint, where at least one of the storage endpoints, such as the first storage endpoint, lacks or has incompatible functionality to perform and manage replication because the storage endpoints have different storage platforms that store data differently, use different control operations and interfaces, etc. Accordingly, replication destination workflow, replication source workflow, and/or a proxy representing the first storage endpoint may be implemented at the second storage endpoint comprising the replication functionality. In this way, replication, such as snapshot replication, may be implemented between the storage endpoints by the second storage endpoint using the replication destination workflow, the replication source workflow, and/or the proxy that either locally executes tasks or routes tasks to the first storage endpoint such as for data access.

A primary storage system appends a red-hot data indicator to each track of data transmitted on a remote data facility during an initial synchronization state. The red-hot data indicator indicates, on a track-by-track basis, whether the data associated with that track should be stored as compressed or uncompressed data by the backup storage system. The red-hot data indicator may be obtained from the primary storage system's extent-based red-hot data map. If the red-hot data indicator indicates that the track should remain uncompressed, or if the track is locally identified as red-hot data, the backup storage system stores the track as uncompressed data. If the red-hot data indicator indicates that the track should be compressed, the backup storage system compresses the track and stores the track as compressed data. After the initial synchronization process has completed, red-hot data indicators are no longer appended to tracks by the primary storage system.

A data storage array is configured for m-way resiliency across a first plurality of storage nodes. The m-way resiliency causes the data storage array to direct each top-level write to at least m storage nodes within the first plurality, for committing data to a corresponding capacity region allocated on each storage node to which each write operation is directed. Based on the data storage array being configured for m-way resiliency, an extra-resilient cache is allocated across a second plurality of storage nodes comprising at least s storage nodes (where s>m), including allocating a corresponding cache region on each of the second plurality for use by the extra-resilient cache. Based on determining that a particular top-level write has not been acknowledged by at least n of the first plurality of storage nodes (where n≤m), the particular top-level write is redirected to the extra-resilient cache.

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.

One or more techniques and/or systems are provided for migrating a trust relationship. For example, a first storage cluster and a second storage cluster have a disaster recovery relationship where the second storage cluster provides failover client access to replicated data, replicated from the first storage cluster to the second storage cluster, in the event the first storage cluster fails. The first storage cluster may have a trust relationship with a third storage cluster, such that data is mirrored from a volume of the first storage cluster into a mirrored volume of the third storage cluster based upon the trust relationship. In the event the first storage cluster fails over to the second storage cluster due to a disaster at the first storage cluster, the trust relationship is migrated to be between the second storage cluster and the third storage cluster for non-disruptive mirroring of data to the mirrored volume.

Failover methods and systems for a storage environment are provided. During a takeover operation to take over storage of a first storage system node by a second storage system node, the second storage system node copies information from a first storage location to a second storage location. The first storage location points to an active file system of the first storage system node, and the second storage location is assigned to the second storage system node for the takeover operation. The second storage system node quarantines storage space likely to be used by the first storage system node for a write operation, while the second storage system node attempts to take over the storage of the first storage system node. The second storage system node utilizes information stored at the second storage location during the takeover operation to give back control of the storage to the first storage system node.

Accelerating segment metadata head scans for storage system controller failover, including: receiving, by a secondary storage unit corresponding to a primary storage unit, a request to store a data segment; storing the data segment and segment metadata at the head of the data segment; and storing, in a data structure, data indicating an erase block storing the segment metadata and indicating an offset in the erase block where the segment metadata is stored.

Techniques are provided for replay of metadata and data operations. During initial execution of operations, identifiers of objects modified by the execution of each operation are identified and stored in association with the operations. When the operations are to be replayed (e.g., executed again, such as part of a replication operation or as part of flushing content from a cache to persistent storage), the identifiers are evaluated to determine which operations are independent with respect to one another and which operations are dependent with respect to one another. In this way, independent operations are executed in parallel and dependent operations are executed serially with respect to the operations from the dependent operations depend.