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: 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 thin device (TDev) is tagged to identify the TDev as being used to access snapshot data on the storage system. If a snapshot is to be shipped to a cloud repository, the tagged TDev is linked to the snapshot, and mounted to a cloud tethering subsystem. When the tagged TDev is linked to the cloud tethering subsystem, the snapshot subsystem reads the thin device tag and, if the thin device is tagged, selectively does not execute a define process on the tagged thin device. By not executing the define process, the tracks of the thin device do not contain metadata identifying the location of the snapshot data on the storage system. Writes to source do not require a private copy of the old data for the snapshot, even if the snapshot is created in a different storage resource pool than the source data volume.

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 thin device (TDev) is tagged to identify the TDev as being used to access snapshot data on the storage system. If a snapshot is to be shipped to a cloud repository, the tagged TDev is linked to the snapshot, and mounted to a cloud tethering subsystem. When the tagged TDev is linked to the cloud tethering subsystem, the snapshot subsystem reads the thin device tag and, if the thin device is tagged, selectively does not execute a define process on the tagged thin device. By not executing the define process, the tracks of the thin device do not contain metadata identifying the location of the snapshot data on the storage system. Writes to source do not require a private copy of the old data for the snapshot, even if the snapshot is created in a different storage resource pool than the source data volume.

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.

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: 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: 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.

Abstract: Techniques for providing snapshots of logical devices may include: receiving a first request to create a first snapshot of a logical device; responsive to the first request, performing first processing including storing first information in a cache slot, the first information identifying the first snapshot and the logical device used as a source of the first snapshot; receiving a second request to activate one or more snapshots, including the first snapshot, identified by information stored in the cache slot; and responsive to receiving the second request, performing second processing including initiating execution of an asynchronous process that performs snapshot activation processing for the one or more snapshots identified by the cache slot.

Abstract: An apparatus in one embodiment comprises at least one processing device having a processor coupled to a memory. The processing device is configured to maintain, for logical storage volumes of a storage system, device sequence numbers for snapshot and extent copy operations. The processing device is also configured to maintain, for at least one track of the logical storage volumes, a track sequence number representing the state of the track with respect to the snapshot and extent copy operations. The processing device is further configured to receive input/output operations directed to the logical storage volumes from host devices coupled to the storage system while at least one snapshot or extent copy operation for the logical storage volumes is in progress, and to utilize the track sequence numbers and the device sequence numbers to determine processing of the received input/output operations while the snapshot or extent copy operations are in progress.

Abstract: An apparatus in one embodiment comprises at least one processing device having a processor coupled to a memory. The processing device is configured to maintain, for logical storage volumes of a storage system, device sequence numbers for snapshot and extent copy operations. The processing device is also configured to maintain, for at least one track of the logical storage volumes, a track sequence number representing the state of the track with respect to the snapshot and extent copy operations. The processing device is further configured to receive input/output operations directed to the logical storage volumes from host devices coupled to the storage system while at least one snapshot or extent copy operation for the logical storage volumes is in progress, and to utilize the track sequence numbers and the device sequence numbers to determine processing of the received input/output operations while the snapshot or extent copy operations are in progress.

Abstract: To allow prompt creation of a target-less snapshot of a target logical volume, after the target logical volume has been linked to a target-less snapshot to allow host access to the target-less snapshot, and prior to all the tracks of the target logical volume being defined with regard to data from the target-less snapshot, a target device sequence number is maintained for the target logical volume, and incremented each time a target-less snapshot is linked to the target logical volume. A target track sequence number is maintained for each track of the target logical volume, and updated each time target-less snapshot data is moved to the corresponding track. The target device sequence number and target track sequence numbers are compared prior to performing host I/O operations directed to the target logical volume to ensure data correctness on a track by track basis.

Abstract: Techniques for providing snapshots of logical devices may include: receiving a first request to create a first snapshot of a logical device; responsive to the first request, performing first processing including storing first information in a cache slot, the first information identifying the first snapshot and the logical device used as a source of the first snapshot; receiving a second request to activate one or more snapshots, including the first snapshot, identified by information stored in the cache slot; and responsive to receiving the second request, performing second processing including initiating execution of an asynchronous process that performs snapshot activation processing for the one or more snapshots identified by the cache slot.

Abstract: A computing environment, such as an data mirroring or replication storage system, may need to process synchronous I/O requests having different priorities in addition to handling I/O requests on the basis of synchronous or asynchronous groupings. The system described herein provides a data storage system that addresses issues involving efficient balancing of response times for servicing synchronous I/O requests having different priorities. Accordingly, the system described herein provides for maintaining an optimal response time for the host-synchronous I/O requests and the optimal throughput of non-host-synchronous I/O requests using a host-synchronous request time window within which processing of non-host-synchronous I/O requests is throttled. The host-synchronous request time window may be selected to enable the optimal response time for the host-synchronous I/O and also to minimize the impact on the overall throughput of the I/O processor of the storage device.

Abstract: A computing environment, such as an data mirroring or replication storage system, may need to process synchronous I/O requests having different priorities in addition to handling I/O requests on the basis of synchronous or asynchronous groupings. The system described herein provides a data storage system that addresses issues involving efficient balancing of response times for servicing synchronous I/O requests having different priorities. Accordingly, the system described herein provides for maintaining an optimal response time for the host-synchronous I/O requests and the optimal throughput of non-host-synchronous I/O requests using a host-synchronous request time window within which processing of non-host-synchronous I/O requests is throttled. The host-synchronous request time window may be selected to enable the optimal response time for the host-synchronous I/O and also to minimize the impact on the overall throughput of the I/O processor of the storage device.