Abstract: A storage system is configured to accept subsequent versions of write data on a given track to multiple respective slots of shared global memory. A track index table presents metadata at the track level, and can hold up to N slots of data. All slots of shared global memory holding data owed to the source volume and to snapshots of the source volume are bound to the track in the track index table. Each time a write occurs on a track, the track index table is used to determine when a write pending slot for the track is owed to a snapshot copy of the storage volume. When a write pending slot contains data that is owed to a snapshot copy of the source volume, a new slot is allocated to the write IO and bound to the track in the track index table.

Abstract: A profile of characteristics of a normal snapshot of a storage object is computed from previous snapshots of the storage object. Characteristics of a new snapshot are compared with the characteristics in the profile to identify an anomaly indicative of a malicious attack. The characteristics include percent data changed between consecutive snapshots, write LBA dispersion, write data reducibility, number and size of writes, write workload profile, and write content profile. The new snapshot is only vaulted or air-gapped if all its characteristics are within ranges defined by the profile.

Abstract: Direct Image Lookup (DIL) metadata is used to perform differential operation for snapshots and linked targets. Each snapshot contains metadata to store “images” to perform direct lookup of user data for any part of any snapshot in the system. Metadata pages of DIL image data represent sets of tracks of data. Metadata pages of subsequent snapshots for the same sets of tracks are compared, and where there are no changes to a given metadata page for a given set of tracks between subsequent snapshot copies, the differential process is not run on the tracks associated with the metadata page. If a given metadata page associated with a set of tracks has changed between subsequent snapshots, the differential process is used to identify which tracks in the subsequent snapshot contain different data than the corresponding tracks of the previous snapshot. Similar differential processing also is implemented for relinked target devices.

Abstract: Generation of new snapshots of a storage object are prompted based on changes to the storage object. An absolute storage change condition is satisfied when the aggregate amount of changed data since the most recent snapshot satisfies a threshold that represents a predefined amount of storage capacity, e.g., N GB. A percentage of used storage change condition is satisfied when the aggregate size of the changes expressed as a percentage of the provisioned storage capacity of snapped storage object satisfies a predetermined threshold, e.g., X % of Y TB. A percentage of provisioned storage change condition is satisfied when the aggregate amount of the changes in terms of percentage of utilized storage capacity of storage object satisfies a predetermined threshold expressed as a percentage of the utilized capacity of the storage object, e.g., P % of Z TB.

Abstract: A first direct index lookup table represents the current state of a storage object using entries with references corresponding to tracks of the storage object. A second direct index lookup table represents a first targetless snapshot of the storage object. A virtual replication data pointer table maps the entries of both the first direct index lookup table and the entries of the second direct index lookup table to backend storage via a system replication data pointer table. Updates to the storage object are represented using new entries in the first direct index lookup table and the system replication data pointer table. Movement of a track that is represented in multiple targetless snapshots that are represented by multiple direct index lookup tables is represented by updating the corresponding virtual replication data pointer table and system replication data pointer table rather than updating each of the direct index lookup tables.

Abstract: Snapsets containing snapshots from a group of storage volumes are assigned snapset IDs. The same snapset ID is applied to each snapshot of the snapset, and is a globally unique value within the storage system. The snapset ID is assigned to a snapshot upon creation, and remains the same regardless of creation or deletion of other snapshots on the storage volume. By assigning a snapset ID to each snapshot of the snapset, and maintaining the snapset ID as a constant value as long as the snapshot is maintained on the storage system, it is possible to easily determine which snapshots form a given snapset. Control operations on particular storage groups or across storage groups are implemented by specifying particular actions to be taken on snapsets or snapshots, which are identified using the snapset IDs.

Abstract: Aspects of the present disclosure relate to improving response rates of input/output (IO) requests targeting undefined virtual storage devices. In embodiments, an (IO request can be received by a storage array. Additionally, a determination of whether the IO request targets an undefined target track can be made. Further, source data related to the IO request can be located. For instance, a direct image lookup (DIL) can be performed to locate the source data. Also, a storage-related operation on the undefined target track can be performed using instructions provided by the IO request, such as updating a version of the undefined track. Further, a storage resource allocation for the undefined target track can be destaged.

Abstract: Aspects of the present disclosure relate to improving response rates of input/output (IO) requests targeting undefined virtual storage devices. In embodiments, an (IO request can be received by a storage array. Additionally, a determination of whether the IO request targets an undefined target track can be made. Further, source data related to the IO request can be located. For instance, a direct image lookup (DIL) can be performed to locate the source data. Also, a storage-related operation on the undefined target track can be performed using instructions provided by the IO request, such as updating a version of the undefined track. Further, a storage resource allocation for the undefined target track can be destaged.

Abstract: Targetless snapshot schedules are defined by policy objects that include a snap creation interval, maximum snap count, and schedule ID. Multiple schedule IDs can be associated with a single storage object to implement different concurrent targetless snapshot schedules with a single storage object. Multiple storage objects may use the same targetless snapshot schedule independently. Because the targetless snapshot schedules are implemented independently, discard of old snapshots to maintain a snap count for a first storage object does not cause discard of snapshots for a second storage object. Further, discard of old snapshots to maintain a snap count for a first schedule does not cause discard of snapshots for a second schedule applied to the same storage object.

Abstract: A target-less point in time image (snapshot) of a storage volume is allowed to be built after activation, by enabling the snapshot data to be modified to create a crash-consistent replica of the source data after the snapshot has been activated. The data of the snapshot remains immutable from a user standpoint, but the snapshot is able to be quickly activated before all of the data of the snapshot has been included in the snapshot, to thus reduce an amount of time IO operations on the source volume are quiesced. A first snapshot of a storage volume is created on a primary storage system and a corresponding second snapshot of the storage volume is activated on a backup storage system before all the data of the first snapshot is received at the backup storage system. Entries of the activated second snapshot are then changed to point to correct back-end allocations.

Abstract: A target-less point in time image (snapshot) of a storage volume is allowed to be built after activation, by enabling the snapshot data to be modified to create a crash-consistent replica of the source data after the snapshot has been activated. The data of the snapshot remains immutable from a user standpoint, but the snapshot is able to be quickly activated before all of the data of the snapshot has been included in the snapshot, to thus reduce an amount of time IO operations on the source volume are quiesced. A first snapshot of a storage volume is created on a primary storage system and a corresponding second snapshot of the storage volume is activated on a backup storage system before all the data of the first snapshot is received at the backup storage system. Entries of the activated second snapshot are then changed to point to correct back-end allocations.

Abstract: Storage objects and targetless snaps of the storage objects are represented using a system replication data pointer table (SRT), direct index lookup (DIL) tables, and virtual replication data pointer tables (VRTs). The SRT is a system level track-based data structure that stores metadata indicative of the actual (physical layer) allocations for all targetless snapshots in a storage array. The size of the SRT in terms of total entries corresponds to the overall storage capacity of the managed drives of the storage array. Each utilized entry of the SRT includes backend metadata with a pointer to a managed drive and metadata that identifies the associated storage object and track via the VRTs and DIL tables. SRT metadata is created and discarded as backend allocations are utilized and freed so the SRT is a dynamic data structure that can efficiently adjust its size and corresponding memory requirements.

Abstract: Targetless snapshots that are in use are excluded from discard and exempted from inclusion against a snapshot retention count limit. Snapshots that are linked to a target volume are considered to be in use. Snapshots having a persist attribute set are considered to be in use. Snapshots having an expiration attribute set are considered to be in use until at least the expiration time. Snapshots having an age limit attribute set are considered to be in use until reaching at least the specified age. The snapshot retention count limit can be updated with a command. Other commands discard snapshots created before a specified time or older than a specified age, provided the snapshots are not in use. A terminate all command prompts discard of all snapshots that are not in use.

Abstract: A snapshot for use in a cascaded snapshot environment includes a device level source sequence number and a Direct Image Lookup (DIL) data structure. The device level source sequence number indicates the level of the snapshot in the cascade, and the snapshot DIL indicates the location of the data within the snapshot cascade. A target device for use in the cascaded snapshot environment includes a device level target sequence number, a track level sequence data structure, and a DIL. When the target device is linked to a snapshot, the device level target sequence number is incremented, which invalidates all tracks of the target device. The snapshot DIL is copied to the target device, but a define process is not run on the target device such that the tracks of the target device remain undefined. IO operations use the device level target sequence number to identify data on the target device.

Abstract: Snapsets containing snapshots from a group of storage volumes are assigned snapset IDs. The same snapset ID is applied to each snapshot of the snapset, and is a globally unique value within the storage system. The snapset ID is assigned to a snapshot upon creation, and remains the same regardless of creation or deletion of other snapshots on the storage volume. By assigning a snapset ID to each snapshot of the snapset, and maintaining the snapset ID as a constant value as long as the snapshot is maintained on the storage system, it is possible to easily determine which snapshots form a given snapset. Control operations on particular storage groups or across storage groups are implemented by specifying particular actions to be taken on snapsets or snapshots, which are identified using the snapset IDs.

Abstract: Snapshot metadata may include a plurality of pages of nodes, including active nodes and free nodes. It may be determined whether a snapshot metadata object is eligible for de-allocation, for example, of one or more of the pages of its snapshot metadata nodes. This determination may be based on a number of free nodes in the snapshot metadata object, for example, in relation to the quantity of nodes that are included in a snapshot metadata page. This determination may be made based on previous usage of the nodes allocated to the snapshot metadata object, for example, the number of active nodes relative to a total size of the snapshot metadata object. For example, a maximum extent of active nodes during one or more periods may be compared to a current extent of active nodes to determine whether the snapshot metadata object is eligible.

Abstract: A snapshot lookup table (SLT) and snapshot pointer structure(s) (SPSs) may be provided for a logical data unit (LSU), each SPS entry corresponding to an LSU data portion and a physical storage location at which data is stored for the data portion for a particular snapshot. A current lookup table (CLT) for a current time may be provided for an LSU, including an entry for each LSU data that points to a respective entry of an SPS. Each time a first write following the creation of a snapshot is made to an LSU data portion, the corresponding CLT entry may be updated to point to the SPS entry that was updated to point to an LSU track table entry. To create a snapshot, a snapshot lookup table (SLT) is created for each snapshot, and the contents of the CLT are copied to the newly created SLT.

Abstract: A snapshot for use in a cascaded snapshot environment includes a device level source sequence number and a Direct Image Lookup (DIL) data structure. The device level source sequence number indicates the level of the snapshot in the cascade, and the snapshot DIL indicates the location of the data within the snapshot cascade. A target device for use in the cascaded snapshot environment includes a device level target sequence number, a track level sequence data structure, and a DIL. When the target device is linked to a snapshot, the device level target sequence number is incremented, which invalidates all tracks of the target device. The snapshot DIL is copied to the target device, but a define process is not run on the target device such that the tracks of the target device remain undefined. IO operations use the device level target sequence number to identify data on the target device.

Abstract: A remote data facility includes a primary storage volume on a first storage system mirrored to a backup storage volume on a second storage system. A nocopy clone of a production volume is added to the primary storage volume. A define process is used to cause the tracks of the nocopy clone to point to backend allocations of tracks of memory of the production volume. As tracks of the nocopy clone are defined, corresponding flags are marked as invalid to cause data associated with the tracks to be replicated across the remote data facility to the backup storage volume. Incremental clones can be added to the primary storage volume, defined, and replicated on the remote data facility using the same process. Nocopy clones and target-less nocopy snapshots of the backup storage volume are used to restore the production volume using failover/failback mechanisms of the remote data facility.

Abstract: A no-copy clone of a logical storage unit is created. A define process is initiated for defining a target logical storage unit as the clone before activation of the target logical storage unit. By initiating the define process before activating the logical storage unit, there is a greater likelihood that, when a write operation is received for a data portion on the source logical storage unit or target logical storage unit after activation of the target LSU, the data portion will already be defined and not need to be defined when performing the write operation. When a write operation is received at the source logical storage unit, if the target logical storage unit is not active yet, the data of the write operation may be written to an allocated physical location for the data portion shared between the source and target logical storage units without updating any clone metadata.