Abstract: In one aspect, IO recovery mechanisms in active/active replication for storage clusters provide, for each write IO request: determining an extent of pages to be modified; acquiring a lock by a cluster local to the request and locally persisting data; atomically creating an entry in a local journal; and sending, by the local cluster, a data write request to a peer cluster. Upon receiving acknowledgement from the peer cluster of successful transmission, the replication journal entry is cleared, the extent is unlocked, and a notification is returned to the peer. In response to a failure event at the peer cluster after persisting the data at the local cluster and creating the journal entry at the local cluster, an aspect includes sending, to the peer cluster upon recovery of the peer cluster, the journal entry with respect to an extent corresponding to a time of the failure event.

Abstract: Described embodiments provide storage system evaluation and comparison processes. An aspect includes sampling data points for a workload running on system over a sampling period. The data points indicate a performance metric with respect to operational characteristics of the system. An aspect further includes subtracting a system specification value from each of the averaged sampled data points, thereby producing deviation values reflecting a deviation of the sampled data points from the system specification value. An aspect also includes averaging the sampled data points, calculating a standard deviation of the averaged sampled data points, and dividing the variance value by the standard deviation, thereby producing a modified performance value that accounts for a deviation in the operational characteristics of the system over the sampling period.

Abstract: An apparatus in an illustrative embodiment comprises at least one processing device comprising a processor coupled to a memory. The processing device detects a drive failure in a first storage system comprising a plurality of drives configured in accordance with a designated redundant array of independent disks (RAID) arrangement, identifies a plurality of data pages to be rebuilt in order to recover from the drive failure, retrieves hash digests of respective ones of the identified data pages, and utilizes the hash digests to request respective corresponding data pages from a second storage system. For each of one or more data pages returned by the second storage system, the processing device utilizes the returned data page as a rebuilt data page in recovering from the drive failure so as to avoid reading multiple data pages from remaining ones of the drives of the designated RAID arrangement to rebuild that data page.

Abstract: A method is used in managing an asynchronous and synchronous transmit priority mechanism. The method receives a plurality of replication requests in conjunction with a replication process, where the plurality of replication requests comprises at least one of a first replication request or a second replication request. A first storage system that comprises a plurality of storage devices is configured to participate in the replication process with a second storage system that comprises a plurality of storage devices. The method optimizes at least one second replication request to optimize processing of the plurality of replication requests.

Abstract: A method is used in managing an asynchronous and synchronous transmit priority mechanism. The method receives a plurality of replication requests in conjunction with a replication process, where the plurality of replication requests comprises at least one of a first replication request or a second replication request. A first storage system that comprises a plurality of storage devices is configured to participate in the replication process with a second storage system that comprises a plurality of storage devices. The method determines an execution order to optimize processing of the plurality of replication requests, where a first replication request execution order that optimizes processing of the at least one first replication request conflicts with optimizing processing of the at least one second replication request.

Abstract: Techniques for processing data include: receiving a hierarchical structure of metadata (MD) pages for a logical device; and performing processing to copy data of the logical device from a source system to a target system. The first processing includes: determining a sequence of the MD pages in accordance with a depth first traversal of the hierarchical structure; defining a cache management policy in accordance with the sequence that indicates when to load the MD pages into a cache and when to remove the MD pages from the cache; loading MD pages into, and removing MD pages from, the cache in accordance with the cache management policy; and copying data pages stored at logical addresses of the logical device in an order in which the logical addresses are accessed using MD pages stored in the cache at various points in time in accordance with the cache management policy.

Abstract: Tiering data between storage media in a content aware storage system is provided. An aspect includes, for each metadata page (MP) of a plurality of MPs: storing a first copy of the MP in a high tier storage, a second copy in an intermediate tier storage, and a third copy in low tier storage. Upon determining, in response to monitoring available space in the high tier storage, usage of the high tier storage exceeds a threshold value, an aspect includes identifying a least recently used (LRU) MP, deleting the LRU MP from the high tier storage, and destaging active entries of a metadata journal for the LRU MP. An aspect further includes receiving a request to read one of the plurality of MPs and, upon determining one of the MPs is the LRU metadata page, an aspect includes reading MP from the intermediate tier storage.

Abstract: A system, computer program product, and computer-executable method of scheduling replication on a data storage system, the system, the computer program product, and computer-executable method including receiving a request to replicate a portion of data stored on the data storage system, dividing the portion of data into a plurality of portions, scheduling replication of each of the plurality of portions, and replicating each of the plurality of portions.

Abstract: A system, computer program product, and computer-executable method of replicating user initiated snapshots created in a distributed system and enabled to be replicated to a remote system, wherein the remote system includes a snapshot tree, the c system, computer program product, and computer-executable method including receiving a request to replicate a first snapshot, determining whether the distributed system is currently replicating a second snapshot, and processing the first snapshot based on the determination.

Abstract: Time addressable storage in a content addressable storage system includes providing a log volume having an index and a journal. For each snapshot, an identifier is entered in the index and a corresponding journal offset is increased. For each write transaction received for a volume, an aspect includes recording a time, address, and hash handle as entries in the journal. Upon receiving a point in time (PIT) for one of the volumes, an aspect includes identifying a most recent snapshot (S) created before the PIT, taking a snapshot (S?) of snapshot (S), identifying a journal corresponding to the snapshot (S) in the index, and reviewing entries of the identified journal up to the PIT. An aspect further includes updating the snapshot (S?) with a corresponding hash handle for each address appearing in the entries until all write transactions before the PIT are contained in the snapshot (S?).

Abstract: An apparatus obtains a set of content-based signatures for respective data pages of at least a portion of at least one storage volume replicated from a source storage system to a target storage system, issues a write for the set of content-based signatures to the target storage system, and reads from a designated location in the target storage system information indicating for each of the content-based signatures whether or not the corresponding data page is present in the target storage system. For one or more data pages not present in the target storage system, the apparatus writes the one or more data pages to respective logical addresses of the replicated storage volume in the target storage system. The issuing of a write, the reading from the designated location, and the writing of the one or more data pages are illustratively performed utilizing respective commands of a standard storage command protocol.

Abstract: A content addressable storage system in one embodiment comprises a plurality of storage devices and a storage controller. The content addressable storage system is configured to receive from another storage system a plurality of snapshots for at least one storage volume designated for backup from the other storage system to the content addressable storage system. For each of a plurality of pages of a given one of the snapshots, the content addressable storage system generates a content-based signature for the page, compares the content-based signature for the page to a previous content-based signature generated for a corresponding page having the same address in a previous one of the snapshots, and stores the page of the given snapshot in one or more of the storage devices of the content addressable storage system responsive to an absence of a match between the compared content-based signatures. The content-based signatures illustratively comprise respective hash handles.

Abstract: An apparatus is configured to generate a current snapshot set for a consistency group comprising a plurality of storage volumes subject to replication from a source storage system to a target storage system, to compare one or more configuration attributes of the current snapshot set to one or more configuration attributes of a previous snapshot set generated for the consistency group, to detect a change in at least one configuration attribute of the current snapshot set relative to the previous snapshot set based at least in part on the comparing, and to communicate the detected change in the configuration attribute from the source storage system to the target storage system so as to permit the target storage system to implement a corresponding configuration update for the consistency group. The generating, comparing, detecting and communicating are illustratively performed as part of an ongoing asynchronous or synchronous replication process carried out between the source and target storage systems.

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: In one aspect, a method includes splitting empty RAID stripes into sub-stripes and storing pages into the sub-stripes based on a compressibility score. In another aspect, a method includes reading pages from 1-stripes, storing compressed data in a temporary location, reading multiple stripes, determining compressibility score for each stripe and filling stripes based on the compressibility score. In a further aspect, a method includes scanning a dirty queue in a system cache, compressing pages ready for destaging, combining compressed pages in to one aggregated page, writing one aggregated page to one stripe and storing pages with same compressibility score in a stripe.

Abstract: A first storage system is configured to participate in a replication process with a second storage system using an active-active configuration. A request for a time-to-live (TTL) grant is received in the first storage system from the second storage system. The first storage system computes an estimate of a difference between local times in the respective first and second storage systems, utilizes the computed estimate in the first storage system to determine a TTL expiration time in the local time in the second storage system, and sends the TTL grant with the TTL expiration time to the second storage system in response to the request. The computed estimate of the difference between the local times in the respective first and second storage systems is illustratively utilized in the first storage system to determine a range for the local time in the second storage system.

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: A first storage system sends a clock synchronization message to a second storage system. The first storage system records a first value of a local time in the first storage system in conjunction with sending the clock synchronization message, and records a second value of the local time in the first storage system in conjunction with receipt of a response to the clock synchronization message from the second storage system. The response comprises a value of a local time in the second storage system. The first storage system computes an estimate of a difference between the local times using the recorded first and second values of the local time in the first storage system and the received value of the local time in the second storage system, and synchronizes the local time in the first storage system with the local time in the second storage using the computed estimate.

Abstract: A storage system in one embodiment comprises a plurality of storage devices and a storage controller. The storage controller is configured to monitor a differential between a storage volume of the storage system and a previous snapshot generated for that storage volume, and responsive to the monitored differential satisfying one or more specified conditions, to generate a subsequent snapshot for the storage volume. For example, monitoring the differential between the storage volume of the storage system and the previous snapshot generated for that storage volume illustratively comprises maintaining a counter indicative of an amount of data in the storage volume that has been written since generation of the previous snapshot. In such an arrangement, generating the subsequent snapshot for the storage volume responsive to the monitored differential satisfying one or more specified conditions illustratively comprises generating the subsequent snapshot responsive to the counter exceeding a specified threshold.

Abstract: A first storage system is configured to participate in a replication process with a second storage system using an active-active configuration. A request for a time-to-live (TTL) grant is received in the first storage system from the second storage system. The first storage system computes an estimate of a difference between local times in the respective first and second storage systems, utilizes the computed estimate in the first storage system to determine a TTL expiration time in the local time in the second storage system, and sends the TTL grant with the TTL expiration time to the second storage system in response to the request. The computed estimate of the difference between the local times in the respective first and second storage systems is illustratively utilized in the first storage system to determine a range for the local time in the second storage system.