Emc IP Holding Company LLC

Dell Products Inc.

Ian Adams

Deepak Vokaliga

Jeffrey Wilson

Bhaskar Bora

Mark J Halstead

Rong Yu

Malak Alshawabkeh

William R Stronge

Benjamin Randolph

Kevin C Heasley

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

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

A primary storage system appends a red-hot data indicator to each track of data transmitted on a remote data facility during an initial synchronization state. The red-hot data indicator indicates, on a track-by-track basis, whether the data associated with that track should be stored as compressed or uncompressed data by the backup storage system. The red-hot data indicator may be obtained from the primary storage system's extent-based red-hot data map. If the red-hot data indicator indicates that the track should remain uncompressed, or if the track is locally identified as red-hot data, the backup storage system stores the track as uncompressed data. If the red-hot data indicator indicates that the track should be compressed, the backup storage system compresses the track and stores the track as compressed data. After the initial synchronization process has completed, red-hot data indicators are no longer appended to tracks by the primary storage system.

Method and apparatus for selective compression of data during initial synchronization of mirrored storage resources

The system, devices, and methods disclosed herein relate to online data expansion in disaster recovery enabled data storage systems. We disclose embodiments that allow storage devices, which are coupled to one another in a disaster recovery, data replication-type scenario, to perform storage expansion in most cases without having to disable remote replication during the expansion. The teachings of this patent application facilitate methods of expansion for data storage device pairings where the data storage devices are the same size or where the primary storage device is smaller than the secondary storage device. In both of these situations, expansion occurs without disabling disaster recovery. In the situation where the secondary storage device is larger than the primary device, expansion is allowed, with the caveat that disaster recovery must be disabled briefly. Moreover, in situations where remote replication is lost or disabled, it is possible to expand a primary or secondary storage device independently, and then to enable expansion of whichever device was not expanded once remote replication is reactivated.

Online data expansion in redundant data storage systems

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Cambridge, MA, United States of America

Ian Adams