Emc IP Holding Company LLC

Dell Products Inc.

Emc Corporation

Jeffrey Wilson

Michael Ferrari

Sandeep Chandrashekhara

Mark J Halstead

Owen Martin

Bhaskar Bora

William R Stronge

Jaeyoo Jung

George F Lettery

Ian Adams

Shruti Gupta

Marik Marshak

Amnon Naamad

Dan Aharoni

Hui Wang

Deepak Vokaliga

Stephen Richard Ives

Andrew Chanler

Peng Yin

James L Davidson

Kevin M Tobin

Ningdong Li

Benjamin Yoder

David T Tsang

Sandeep Chandrashekara

Sanjay Narahari

Deepika Hegde

Manickavasasaham M Senghuden

Art Longden

Mordechai Grutman

Guruprasad Pattar

Ben Yoder

Two storage arrays, a primary storage array and a remote storage array, are configured to implement a remote data replication facility, in which both the storage arrays are active, such that hosts can both read and write data to both the primary storage array and remote storage array. If the host would like to add storage, the host sends a command to one of the storage arrays to add a storage volume. The first storage array that receives the command locally creates the requested storage volume and coordinates with the second storage array to also locally create the requested storage volume. While the storage volumes are being created and formatted, the first and second storage arrays coordinate status responses to the host. Once the requested storage volumes is ready on both storage arrays, the storage volume is made accessible to the host on both storage arrays.

Storage volume addition to synchronized read/write accessible storage systems

Unmap extents transmitted in delta sets are used to unmap LBAs on remote replicas of asynchronously replicated storage objects. A host server sends a SCSI unmap command to a production storage array to unmap a range of logical block addresses. In response, the production storage array creates an unmap extent that identifies the local and remote replicas, starting LBA, and number of LBAs to be unmapped. At the end of each asynchronous replication cycle, unmap extents and updated data are sent to a disaster recovery storage array in a delta set that preserves chronological ordering. The disaster recovery storage array receives the delta set and discards cached data corresponding to the unmapped LBAs indicated in the unmap extents and de-allocates the backend storage space. Integrating unmap extents with updated data in delta sets maintains point-in-time consistency and is more efficient than sending zero data.

Unmapping logical block addresses of remote asynchronously replicated volumes

Receipt of an Xcopy command to copy data between storage objects that are both mirrored by a remote storage system prompts a local storage system to generate a remote Xcopy to prompt the remote storage system to copy the data between the remote mirrors of the storage objects, thereby avoiding transmission of the data from the local storage system to the remote storage system. If there are write-pendings or invalids on the tracks designated by the local Xcopy, then the associated data is sent to the remote storage system. Similarly, the associated data is sent if the code levels of the local and remote storage systems are incompatible.

Remote replication data efficiency optimization with host extended copy commands

Snapshots from a first LSU (R1) on a first storage system (A1) may be replicated to a second replica LSU (R2) on a second storage system (A2), for example, concurrently to remotely replicating (e.g., synchronously) write operations for R1 to R2. A process, P, on A1 executing the replication of the snapshots from R1 to R2 may be a separate process than the one or more processes on A1 executing remote replication of write operations for R1 to R2. During a consistency window on A1, outstanding write operations for R1 at the time the consistency window opened may be logged, and a pair of snapshots, SS1and SS1may be activated on R1 and R2, respectively. After the consistency window has closed, the SS1snapshot metadata and snapshot data may be updated based on the outstanding write operations.

Synchronous remote replication of snapshots

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.

Targetless snapshot virtual replication data pointer table

Snapshots may be remotely replicated asynchronously from a first LSU (R) on a first storage system (A) to a second replica LSU (R) on a second storage system (A). The storage system Amay open a consistency window to suspend initiating processing of new write operations received on A. While the consistency window is open, Amay: take a first snapshot, SS, of R; record, in association with the first replication cycle, an indication to replicate SSon A; and initiate a next replication cycle to record write operations of the next new write requests to be received from hosts. After initiating a next replication cycle, Amay close the consistency and transmit the first replication cycle to A. Amay apply the write operations of the first replication cycle to R, and then take a second snapshot SSof R, which should be a replica of SS.

Asynchronous remote replication of snapshots

Embodiments of the present disclosure relate to autonomous data protection. An input/output (I/O) stream can be received for a storage device. One or more anomalies corresponding to the I/O stream can be identified. At least one of the one or more anomalies can be offloaded anomalies to a remote storage based on a capacity of memory allocated to store at least one snapshot of the storage device that include at least one of the one or more anomalies.

Autonomous data protection

A model of an algorithm to be tested is created based on the steps that the algorithm uses to implement a particular function. The model is used by an algorithm verification process to control execution of the application under test. Stubs (small pieces of code) are inserted into the application under test which are used to control execution of the algorithm to determine the result of execution of the algorithm at various locations. The remote stubs enable the testing framework to control execution of the application, stop execution of the application, view data structures associated with the application, freeze system behavior, induce multi-layered dependent sequences, analyze logs, change system flow based on test requests, examine internal data structures as part of the tests, and verify that each method and the combined results of the methods are as expected, based on the original definition of the application algorithm.

Automated algorithmic verification in an embedded complex distributed storage environment

Snapshots of a first logical storage unit (LSU) (R1) on a first storage system (A1) may be taken while replication is inactive between A1 and a second storage system (A2), such that these outstanding snapshots are not replicated to a second replica LSU (R2) on A2. Upon replication becoming active, the outstanding snapshots may be replicated to R2 without disrupting or impairing the remote replication of write operations between R1 and R2 as part of standard remote replication. A process on A1 executing the replication of the outstanding snapshots from R1 to R2 may be a separate process than one or more processes on A1 executing standard remote replication including the replication of write operations from R1 to R2. The process may be given low priority on A1 so as to not impair performance of other operations, including standard remote replication and replicating outstanding write operations on A1.

Remote replication of snapshots taken while replication was inactive

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.

Modifying data of activated target-less point-in-time images of storage volumes

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.

Targetless snapshot system replication data pointer table

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.

Consistent IO performance on undefined target devices in a cascaded snapshot environment

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.

Efficient memory usage for snapshots based on past memory usage

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.

Snapshot metadata management

Providing automated targetless snapshots for storage volumes includes estimating storage space needed for a new set of the snapshots based on an amount of expected change of data on the storage volumes, deleting current snapshots to free up an amount of space corresponding to estimated storage space for the new set of the snapshots, and creating the new set of the snapshots. The current snapshots may be selected for deletion based on creation date of the snapshots. Snapshots with an oldest creation data may be deleted. The storage volumes may be provided on a storage system. The storage system may show storage space used by the snapshots as unallocated. Storage space used by the snapshots may be managed by a storage resource pool. The storage resource pool may convert storage space shown as unallocated into allocated storage space in response to snapshots provided therein being converted into accessible snapshots.

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Franklin, MA, United States of America

Jeffrey Wilson