Abstract: An apparatus includes at least one processing device comprising a processor coupled to a memory, with the processing device being configured to identify a first storage volume of a first snapshot group of a storage system, to identify a second storage volume that is not part of the first snapshot group of the storage system but contains at least a threshold amount of matching data relative to the first storage volume, and to merge the second storage volume into the first snapshot group. The processing device illustratively comprises a storage controller of the storage system. The storage system may be implemented as a clustered storage system comprising a plurality of storage nodes. Each storage node may comprise a set of processing modules of a distributed storage controller of the clustered storage system.

Abstract: A distributed storage system comprises a first module and a second module. The first module processes read requests for an address range, to send to the second module. The first module receives an address associated with a read request for a data page stored on the second module. A method searches a table on the first module for a content-based signature of the data page based on the address and provides the data page from a first module read cache if the content-based signature is in the read cache, where content-based signatures in the table are associated with the address range.

Abstract: A storage system comprises a plurality of storage nodes each comprising one or more storage devices and a processor coupled to a memory. The storage system is configured to store data blocks across the storage devices of the storage nodes utilizing a redundant array of independent disks (RAID) arrangement. At least a given one of the storage nodes is configured to store a plurality of RAID metadata bitmaps in persistent storage of the storage node so as to be available for a recovery operation in the event of a detected failure, to identify a particular subset of the RAID metadata bitmaps to be updated in conjunction with an additional operation other than the recovery operation, and to temporarily store the identified subset of the RAID metadata bitmaps in the memory of the storage node in a manner determined based at least in part on an operation type of the additional operation.

Abstract: A method is used in managing asynchronous replication. The method receives a multi-page replication request in conjunction with the replication process, where the first storage system comprises a plurality of storage devices and the second storage system comprises a plurality of storage devices. The method determines at least one replication condition meets a threshold. In response, the method optimizes the multi-page replication request to optimize the replication process.

Abstract: In one aspect, extent lock resolution for storage devices includes designating one of the storage devices as a lock winner, which takes priority over another storage device over a lock. An aspect also includes receiving a replication request issued, by a host during active/active replication, determining an extent of pages to be modified by the request, locking the extent in local storage device, and executing the request at the local device. An aspect also includes sending a write request to a remote device. If the remote device is the designated lock winner, and an attempt to lock the extent is unsuccessful, the remote device waits for the lock to become available. If the remote device is not the designated lock winner, and an attempt to lock the extent is unsuccessful, the remote device rejects the write request and sends a request to the local device to resend the write request.

Abstract: In one aspect, implementing enhanced QoS for multiple replication sessions in a replication setup includes, for each of a number of replication sessions simultaneously implemented via the storage system, determining an assigned priority level and calculating a corresponding resource profile. The resource profile specifies a minimum required amount of bandwidth and a minimum amount of input/output (IO) operations for the replication session. An aspect also includes determining available system resources for an aggregate of the replication sessions. The available system resources indicate a maximum available amount of bandwidth and a maximum available IO rate across the storage system. An aspect further includes apportioning resources among the replication sessions as a function of collective priority levels, resource profiles, and the available system resources.

Abstract: A processing device identifies a first snapshot to be split from a first snapshot group, generates a second snapshot of the first snapshot, continues write operations to the first snapshot, copies the second snapshot to a storage volume of a second snapshot group, and computes a differential between the first and second snapshots. Responsive to the differential between the first and second snapshots being above a specified threshold, an additional snapshot of the first snapshot is generated, a differential is computed between the additional snapshot and a previous snapshot of the first snapshot, and if necessary the generating of an additional snapshot and the computing of a differential are repeated one or more additional times, until the differential is at or below the specified threshold. The processing device updates the storage volume based at least in part on one or more of the computed differentials.

Abstract: In one aspect, implementing enhanced QoS for multiple replication sessions in a replication setup includes, for each of a number of replication sessions simultaneously implemented via the storage system, determining an assigned priority level and calculating a corresponding resource profile. The resource profile specifies a minimum required amount of bandwidth and a minimum amount of input/output (IO) operations for the replication session. An aspect also includes determining available system resources for an aggregate of the replication sessions. The available system resources indicate a maximum available amount of bandwidth and a maximum available IO rate across the storage system. An aspect further includes apportioning resources among the replication sessions as a function of collective priority levels, resource profiles, and the available system resources.

Abstract: In one aspect, provenance-based replication includes assigning a GUID to a first snap tree of a first storage array and another GUID to a second snap tree of a second storage array. The trees are peers of each other with respect to at least one volume replicated between the arrays. For each volume in the first array that is replicated to a volume in the second array, an aspect includes assigning a volume pairing identifier common to both volumes. Upon determining data for a volume (V1) in the first array has been lost/corrupted, an aspect includes identifying the peer tree from the GUID and using the pairing ID of V1 to search the peer tree for a volume (V2) in the second array, retrieving data for V2, computing a delta between the data of V1 and the data of V2, and reconstructing the lost/corrupted data for V1 using the delta.

Abstract: An apparatus includes at least one processing device comprising a processor coupled to a memory, with the processing device being configured to identify a first storage volume of a first snapshot group of a storage system, to identify a second storage volume that is not part of the first snapshot group of the storage system but contains at least a threshold amount of matching data relative to the first storage volume, and to merge the second storage volume into the first snapshot group. The processing device illustratively comprises a storage controller of the storage system. The storage system may be implemented as a clustered storage system comprising a plurality of storage nodes. Each storage node may comprise a set of processing modules of a distributed storage controller of the clustered storage system.

Abstract: In one aspect, performing dynamic balancing of input/output (IO) operations includes providing a first queue for a first storage unit and a second queue for a second storage unit. The queues are configured to receive IO requests directed to the storage units, An aspect also includes determining a quality of service (QoS) value assigned to each of the storage units, pulling entries from the queues at a rate that accords with the QoS value, executing IOs, and monitoring bandwidth of the IO operations. Upon determining the bandwidth is not in alignment with the QoS value for either of the first and second storage units, a further aspect includes modifying the rate in which entries are pulled from at least one of the queues, continuing the monitoring the bandwidth and the modifying the rate until the bandwidth aligns with the QoS value assigned to each of the storage units.

Abstract: In one aspect, implementing a link selection protocol in a replication setup includes sending, by a control module to a selected routing module of a plurality of routing modules, an IO request and IO requirements to process the request. The IO requirements include an amount of data subject to the replication IO request and a latency requirement subject to the replication IO request. A further aspect includes comparing, by the selected routing module, the IO requirements to link status information of each of a plurality of links; selecting, by the selected routing module, one of the links assigned to the selected routing module as a function of the IO requirements and the link status information; and executing the IO request over the selected one of the links.

Abstract: An apparatus in one embodiment comprises a first storage system having a plurality of storage devices. The first storage system is configured to participate in a replication process with a second storage system. The first storage system comprises a replication engine configured to request from a data module of the first storage system at least one data page to be replicated to the second storage system as part of the replication process. If the requested data page is already available in compressed form in the data module, the replication engine receives the requested data page in compressed form and transmits it to the second storage system along with at least a portion of a content-based signature of the requested data page. If the requested data page is not already available in compressed form in the data module, the replication engine receives the requested data page in uncompressed form and transmits it to the second storage system.

Abstract: An apparatus in one embodiment comprises at least one processing device comprising a processor coupled to a memory. The processing device is configured to establish an initial assignment of a plurality of counters to leaf nodes of a tree structure where each such leaf node represents a particular block size, to monitor count values of respective ones of the counters associated with the leaf nodes, to split at least a given one of the leaf nodes into multiple leaf nodes, each representing a block size smaller than the particular block size, responsive to the monitored count for its corresponding counter exceeding a split threshold, the given leaf node thereby being transformed into a non-leaf parent node of the multiple leaf nodes, and to modify the assignment of the plurality of counters to the leaf nodes responsive to the splitting. The multiple leaf nodes may be subsequently merged to recreate the given leaf node.

Abstract: A storage system in one embodiment comprises a plurality of storage devices and a storage controller. The storage system implements a loopback replication process in which one or more source storage objects are replicated to one or more corresponding target storage objects within the storage system. The storage system obtains a pairing identifier, pairs a source storage object with a target storage object by associating respective distinct instances of the pairing identifier with the source storage object and the target storage object, and replicates the source storage object to the target storage object based at least in part on the associated instances of the pairing identifier. Each of the source and target instances of the pairing identifier comprises a collision field. The collision fields of the source and target instances of the pairing identifier have respective distinct values in order to prevent collisions between the source and target storage objects during loopback replication.

Abstract: An apparatus in one embodiment comprises a storage system including multiple storage nodes each having a plurality of storage devices. Each of the storage nodes further comprises a set of processing modules configured to communicate with corresponding sets of processing modules on other ones of the storage nodes. The sets of processing modules of the storage nodes collectively comprise at least a portion of a distributed storage controller of the storage system. The distributed storage controller is configured to implement token-based data flow control between designated ones of the modules by determining a token distribution for the designated modules, the token distribution providing an allocation of tokens to particular ones of the designated modules. A given one of the modules is configured to limit its generation of messages to other modules based at least in part on availability of corresponding ones of the tokens allocated to the given module.

Abstract: A first storage system is arranged in an active-active configuration with a second storage system. The first storage system receives from a host device a first command of a multiple-command token-based data transfer, the first command specifying a source extent of a storage volume. The first storage system suspends all writes to the storage volume in the first storage system; directs the second storage system to suspend all writes to the storage volume in the second storage system; takes a snapshot of the storage volume in the first storage system; directs the second storage system to take a snapshot of the storage volume in the second storage system; associates a token with the source extent of the storage volume and the snapshot in the first storage system; sends the token to the second storage system; and directs the second storage system to associate the token with the source extent of the storage volume and the snapshot in the second storage system.

Abstract: An apparatus in one embodiment comprises a storage system having a plurality of storage devices configured to store at least a first set of data. The storage system is configured to generate a first signature for the first set of data and to verify equivalence between the first set of data and a second set of data by comparing the first signature to a second signature generated for the second set of data. The first and second sets of data comprise respective first and second sets of pages with each page having a content-based page identifier and a page address, and the first and second signatures are generated as respective functions of the page identifiers and page addresses of the respective first and second sets of pages. The first and second sets of data may comprise respective first and second storage volumes, respective first and second sets of multiple storage volumes, or other sets of data.

Abstract: A response is made to a request to replicate, from a production system to a plurality of target systems, a page of data, having an associated short hash. A replication session is established for each target system to replicate the page of data to the target systems. If it's the first request for the short hash, then the page of data associated with the short hash is received and stored in a physical cache. If it's not the first request, then the page of data from the physical cache is retrieved; and, based on dynamic tracking of when each replication sessions requests the page of data based on the short hash, the page of data from the physical cache is cleared when all of the replication sessions have requested the page of data based on the short hash and have accessed the page of data.

Abstract: In one aspect, support for hash based xcopy replication for synchronous replication is provided. An aspect includes determining, in response to an xcopy command, whether a source logical unit (LU) and a target LU are in active synchronous replication to the same target site. Upon determining that the LUs are in active synchronous replication, increasing a count of a hash handle list, obtaining a unique full hash digest, and sending the digest with volume replication pairing identifier, offset, and length to the target. Upon receiving a request from the source, searching, by the target, for local hash handles of the digest; and upon determining the local hash handles exist in the digest, incrementing, the reference counter handle list, and sending corresponding hash handles from the source site to the target.