In example implementations, unreferenced memory addresses in a segment of a storage volume may be identified. Access to the segment of the storage volume may be controlled by one of a plurality of storage volume controllers (SVCs). The plurality of SVCs may control access to respective segments of the storage volume. Indicators of the identified unreferenced memory addresses may be stored in a volatile memory in the one of the plurality of SVCs. In response to an input/output (I/O) command from a host, data may be written to one of the identified unreferenced memory addresses corresponding to one of the indicators stored in the volatile memory. After the data has been written, the one of the indicators may be deleted from the volatile memory. The one of the identified unreferenced memory addresses may not have been made available to other SVCs after being identified.

An apparatus includes at least one processing device comprising a processor coupled to a memory, with the processing device being configured to maintain at least first and second journals for respective first and second different types of input-output requests, to move one or more entries between the first journal and the second journal under one or more specified conditions, to perform a clean-up operation for at least one of the first and second journals in conjunction with the moving of the one or more entries, and responsive to a failure occurring during the clean-up operation, to execute a contention resolution algorithm to resolve logical address range lock contentions between different entries of the first and second journals. The processing device illustratively comprises a storage controller of a storage system. The storage system may be, for example, a source storage system configured to carry out a synchronous replication process with a target storage system.

A first control unit of a first control device executes: a synchronous copy process for writing data from a host device into a first storage medium, transmitting the data to a second control device, and replying to the host device; a storage process for storing the data written in the first storage medium into a first region, instructing the second control device on a buffer switch when a predetermined condition is satisfied, and switching a storage destination to a second region; and an asynchronous copy process for transmitting the data in the first region and the second region to a third control device at a time, respectively. A second control unit stores the data transmitted from the first control unit in a second storage medium and a third region, and when the buffer switch is instructed, stores the data in the second storage medium and a fourth region.

Servicing I/O operations directed to a dataset that is synchronized across a plurality of storage systems, including: receiving, by a follower storage system, a request to modify the dataset; sending, from the follower storage system to a leader storage system, a logical description of the modification to the dataset; receiving, from the leader storage system, information describing the modification to the dataset; processing, by the follower storage system, the request to modify the dataset; receiving, from the leader storage system, an indication that the leader storage system has processed the request to modify the dataset; and acknowledging, by the follower storage system, completion of the request to modify the dataset.

The present disclosure provides a method, system, and device for security object synchronization at multiple nodes of an active-active environment. To illustrate, a source node may generate a corresponding security object sync request for each of multiple target nodes. The source node may send the security object sync request to the target nodes via a source queue and, for each target node, a corresponding distribution queue. A distribution queue may be closed based on an acknowledgement received from a corresponding target node, after a time period, or after a number of transmission attempts. A synchronization log may be maintained to indicate which security object sync requests have been delivered to which target nodes. In some implementations, the source node and the target nodes are part of an active-active environment that may be synchronized in time so the nodes resolve conflicts between received security object updates initiated from two different nodes.

One or more techniques and/or computing devices are provided for utilizing snapshots for data integrity validation and/or faster application recovery. For example, a first storage controller, hosting first storage, has a synchronous replication relationship with a second storage controller hosting second storage. A snapshot replication policy rule is defined to specify that a replication label is to be used for snapshot create requests, targeting the first storage, that are to be replicated to the second storage. A snapshot creation policy is created to issue snapshot create requests comprising the replication label. Thus a snapshot of the first storage and a replication snapshot of the second storage are created based upon a snapshot create request comprising the replication label. The snapshot and the replication snapshot may be compared for data integrity validation (e.g., determine whether the snapshots comprise the same data) and/or quickly recovering an application after a disaster.

A system and method include migrating, by a migration controller, a first entity of a first subset of entities from a source site to a target site in a virtual computing system based on an asynchronous mode of replication. The system and method also include replicating, by the migration controller, data of a second entity of a second subset of entities from the source site to the target site based on a synchronous mode of replication in parallel with the migration of the first entity for dynamically adjusting a recovery time objective parameter.

Architectures and techniques are described that can enhance the functionality of a witness for an active-active storage array. In the event of a dual storage area network (SAN) failure, or another suitable event, host-array connectivity can take precedence for the witness in determining a winner or loser. Techniques are presented to identify connectivity issues and to utilize connectivity data in connection with determining a winner or a loser.

One or more techniques and/or computing devices are provided for synchronous replication. For example, synchronous replication relationships are established between a first storage object (e.g., a file, a logical unit number (LUN), a consistency group, etc.), hosted by a first storage controller, and a plurality of replication storage objects hosted by other storage controllers. In this way, a write operation to the first storage object is implemented in parallel upon the first storage object and the replication storage objects in a synchronous manner, such as using a zero-copy operation to reduce overhead otherwise introduced by performing copy operations. Reconciliation is performed in response to a failure so that the first storage object and the replication storage objects comprise consistent data. Failed write operations and replication write operations are retried, while enforcing a single write semantic. Dependent write order consistency is enforced for dependent write operations, such as overlapping write operations.

One or more techniques and/or computing devices are provided for utilizing snapshots for data integrity validation and/or faster application recovery. For example, a first storage controller, hosting first storage, has a synchronous replication relationship with a second storage controller hosting second storage. A snapshot replication policy rule is defined to specify that a replication label is to be used for snapshot create requests, targeting the first storage, that are to be replicated to the second storage. A snapshot creation policy is created to issue snapshot create requests comprising the replication label. Thus a snapshot of the first storage and a replication snapshot of the second storage are created based upon a snapshot create request comprising the replication label. The snapshot and the replication snapshot may be compared for data integrity validation (e.g., determine whether the snapshots comprise the same data) and/or quickly recovering an application after a disaster.