Abstract: A storage system comprises multiple storage nodes each comprising at least one storage device. Each of the storage nodes further comprises a set of processing modules configured to communicate over one or more networks with corresponding sets of processing modules on other ones of the storage nodes. The sets of processing modules of the storage nodes each comprise at least one data module and at least one control module. The storage system is configured to assign portions of a content-based signature space of the storage system to respective ones of the data modules, and to assign portions of a logical address space of the storage system to respective ones of the control modules. The assignment of portions of the logical address space to the control modules is configured to at least partially offset an unbalanced condition between local physical storage capacities of the data modules.

Abstract: An apparatus in one embodiment comprises at least one processing device comprising a processor coupled to a memory, with the processing device being configured to obtain content-based signatures for respective data pages of at least one write operation, to send the content-based signatures to a content addressable storage (CAS) system, and to receive from the CAS system information indicating for each of the content-based signatures whether or not the corresponding data page is present in the CAS system. Responsive to the information received from the CAS system indicating that one or more of the corresponding data pages are not present in the CAS system, the processing device sends the one or more corresponding data pages to the CAS system. The processing device illustratively comprises a host device coupled to the CAS system over a network.

Abstract: Techniques for determining unique ownership of data blocks includes selecting a first data block referenced by a first logical address of a first logical device, wherein first metadata for the first data block includes a reference count and a result used in determining sole unique ownership of the first data block; determining C1, an expected value of the result of the first metadata when the first logical device is a sole unique owner of the first data block; and performing first processing that determines whether the first logical device is the sole unique owner of the first data block. The first processing includes: determining whether C1 equals a current value of the result of the first metadata; and determining that the first logical device is the sole unique owner of the first data block if C1 equals the current value of the result of the first metadata.

Abstract: A storage system in one embodiment comprises a plurality of storage devices and an associated storage controller. The storage controller is configured to identify a dataset to be scanned to generate a capacity release estimate for prospective deletion of that dataset, to designate a content-based signature prefix to be utilized in the scan, and to scan logical address mapping information for the dataset to identify one or more pages of the dataset that have the designated content-based signature prefix. The scanning further comprises, for each such identified page, determining a reference count of the page, and responsive to the reference count of the page having a particular value, determining a compressibility measure for the page. The storage controller generates the capacity release estimate for prospective deletion of the dataset based at least in part on the one or more page compressibility measures determined as part of the scan.

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 detect an error relating to storage of a given data page in a first storage system, and to send a message to at least one additional storage system, the message containing a hash handle of the given data page with the hash handle having a length that is shorter than that of a corresponding hash digest of the given data page. The processing device is further configured to receive from the additional storage system responsive to the message a recovery data page identified by the additional storage system as having the same hash handle as the given data page. Separate instances of the message containing the hash handle of the given data page may be sent to each of a plurality of additional storage systems.

Abstract: A method, computer program product, and computer system for receiving, by a target sent from a source, a first hash signature associated with a page of data. It may be determined that the first hash signature exists on the target. The target may receive a second hash signature sent from the source associated with the page of data. A third hash signature may be generated at the target. It may be determined that the second hash signature matches the third hash signature indicating the page of data exists on the target. A data-less write command may be executed using the page of data existing on the target to deduplicate the page of data existing on the target.

Abstract: A method, computer program product, and computer system for invalidating, by a target, all data in a first volume. A source may scan a hash to address table for a second volume to be migrated to the first volume. Data in the second volume may be migrated to be stored in the first volume by pushing information from the hash to address table to the target.

Abstract: An aspect includes implementing capacity reduction in a storage system includes for each of a candidate page and a target page in the storage system, identifying a subset of sectors having identical data or a minimum amount of non-identical data, performing a bit-wise exclusive OR (XOR) operation on sectors of the candidate page and the target page, determining entropy from results of the XOR operation. Upon determining the entropy is less than or equal to a threshold value, an aspect includes building a reference page from an XOR sector containing results of the bit-wise XOR operation, and performing a compression operation on the reference page.

Abstract: Techniques for performing cache management may include: partitioning entries of a hash table into buckets, wherein each of the buckets includes a portion of the entries of the hash table; configuring a cache, wherein said configuring includes allocating a section of the cache for exclusive use by each bucket; and performing first processing that stores a data block in the cache. The first processing may include: determining a hash value for a data block; selecting, in accordance with the hash value, a first bucket of the plurality of buckets, wherein a first section of the cache is used exclusively for storing cached data blocks of the first bucket; storing metadata used in connection with caching the data block in a first entry of the first bucket; and storing the data block in a first cache location of the first section of the cache.

Abstract: An apparatus comprises a storage system having storage devices and an associated storage controller. In conjunction with initiation of a checkpoint, the storage controller sets a checkpoint started flag for the checkpoint, marks user data pages and metadata pages for write operations already entered in a write journal of the storage system as of the setting of the checkpoint started flag as checkpoint pages, and marks user data pages and metadata pages for new write operations entered in the write journal after the setting of the checkpoint started flag as non-checkpoint pages by altering information used to generate signatures for respective ones of the metadata pages. Metadata pages characterizing the same user data pages subject to write operations at different times thereby have different signatures depending on whether or not the checkpoint started flag was set when its corresponding write operation was entered in the write journal.

Abstract: An apparatus in one embodiment comprises at least one processing device comprising a processor coupled to a memory, with the processing device being configured to obtain content-based signatures for respective data pages of at least one write operation, to send the content-based signatures to a content addressable storage (CAS) system, and to receive from the CAS system information indicating for each of the content-based signatures whether or not the corresponding data page is present in the CAS system. Responsive to the information received from the CAS system indicating that one or more of the corresponding data pages are not present in the CAS system, the processing device sends the one or more corresponding data pages to the CAS system. The processing device illustratively comprises a host device coupled to the CAS system over a network.

Abstract: An apparatus includes at least one processing device comprising a processor coupled to a memory, with the processing device being configured to maintain a synchronous replication input-output (IO) request list having a plurality of entries corresponding to respective synchronous replication IO requests, a given such entry identifying at least a sender component and one or more address locks held by the corresponding synchronous replication IO request. The processing device is further configured to detect a failure of a particular one of a plurality of sender components, to access the synchronous replication IO request list to identify one or more address locks held by at least one synchronous replication IO request previously sent by the failed sender component, and to release one or more address lock waiters that are waiting to obtain the one or more identified address locks. Other embodiments include methods and computer program products.

Abstract: An apparatus includes at least one processing device comprising a processor coupled to a memory, with the processing device being configured to maintain a synchronous replication input-output (IO) request list having a plurality of entries corresponding to respective synchronous replication IO requests, a given such entry identifying at least a sender component and one or more associated component resources to be released responsive to a failure of the sender component. The processing device is further configured to detect a failure of a particular one of a plurality of sender components, to access the synchronous replication IO request list to determine one or more associated component resources to be released, to release the one or more associated component resources, and to update the synchronous replication IO request list by marking the one or more associated component resources as released. Other embodiments include methods and computer program products.

Abstract: Techniques for providing a direct IO path to compressed data on storage media of a storage system. The techniques include triggering a transaction cache to perform a flush operation for updating mapping metadata for a storage object containing the compressed data. Having updated the mapping metadata for the storage object, the techniques further include issuing, by a copier module, an IO read request for the compressed data of the storage object to a namespace layer, which issues the IO read request to a mapping layer. The techniques further include forwarding the IO read request to a logical layer of the mapping layer, bypassing the transaction cache. The techniques further include reading, by the logical layer, the compressed data of the storage object from the storage media, and providing, via the mapping layer and the namespace layer, the compressed data to the copier module for transfer to a destination storage system.

Abstract: A storage system comprises a plurality of storage nodes each comprising one or more storage devices. Each of the storage nodes further comprises a processor coupled to a memory. The storage system is configured to prefill a given stripe across multiple ones of the storage devices with data blocks to a first fullness level, to designate at least a subset of the prefilled data blocks of the stripe as available for use in prefilling one or more logical storage volumes of the storage system, and to prefill a given one of the logical storage volumes to a second fullness level utilizing selected ones of the available data blocks. The given stripe across multiple ones of the storage devices illustratively comprises a RAID stripe.

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 identify a dataset to be scanned to generate a deduplication estimate for that dataset, to designate a subset inclusion characteristic to be utilized in the scan, and for each of a plurality of pages of the dataset, to scan the page, where scanning the page includes computing a polynomial-based signature for the page, determining whether or not the polynomial-based signature satisfies the designated subset inclusion characteristic, and responsive to the polynomial-based signature satisfying the designated subset inclusion characteristic, computing a content-based signature for the page and updating a corresponding entry of a deduplication estimate table for the dataset based at least in part on the content-based signature.

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 identify a dataset to be scanned to generate a deduplication estimate for that dataset, to designate a content-based signature prefix to be utilized in the scan, and for each of a plurality of pages of the dataset, to scan the page, where scanning the page includes computing a content-based signature for the page, comparing an initial portion of the content-based signature to the designated content-based signature prefix, and responsive to a match between the initial portion and the designated content-based signature prefix, updating a corresponding entry of a deduplication estimate table for the dataset. The processing device generates the deduplication estimate for the dataset based at least in part on contents of the deduplication estimate table.

Abstract: A method, computer program product, and computer system for receiving, by a computing device, new data to write to a leaf. At least two timestamps of the leaf may be examined. It may be determined whether a time interval between the at least two timestamps of the leaf is greater than an age threshold. The new data may be written to a first tier storage device when the time interval between the at least two timestamps of the leaf is less than the age threshold; The new data may be written to a second tier storage device when the time interval between the at least two timestamps of the leaf is greater than the age threshold.

Abstract: A method, computer program product, and computing system for identifying a potential deduplication candidate and a related deduplication target; executing a comparison operation with respect to the potential deduplication candidate and the related deduplication target to generate a comparison result; and determining a level of similarity between the potential deduplication candidate and the related deduplication target by processing the comparison result.

Abstract: An aspect of dynamic physical capacity allocation in an unbalanced content-addressable storage system includes initiating a scale up for a storage cluster. An aspect further includes determining a target number of hash-to-physical-location-on-disk (h2d) slices to be assigned to each data module (D module), and reassigning h2d slices assigned to D modules having greater than the target number of h2d slices to D modules having less h2d slices than the target number.