Remote replication of snapshots taken while replication was inactive

Patent metadata

Field	Value
Publication number	US-11513900-B2
Application number	US-202117237100-A
Country	US
Kind code	B2
Filing date	Apr 22, 2021
Priority date	Apr 22, 2021
Publication date	Nov 29, 2022
Grant date	Nov 29, 2022

Abstract

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.

First claim

What is claimed is:

1. For a system including a first storage system, a second storage system, and a first logical storage unit, wherein the first storage system is configured to replicate data of the first logical storage unit to a second logical storage unit on the second storage system, a method comprising:
recording a list of a plurality of snapshots of the first logical storage unit that were taken on the first storage system but not replicated to the second storage system because of a first period of time during which the replication of the first logical storage unit to the second logical storage unit is inactive; and
in response to the replication of the first logical storage unit to the second logical storage unit becoming active, accessing the list and replicating the plurality of snapshots of the list from the first storage system to replica snapshots on the second storage system,
wherein the replicating of the plurality of snapshots is performed concurrently to replicating write operations as part of the replication of the first logical storage unit to the second logical storage unit.

2. The method of claim 1 , wherein the replicating of the plurality of snapshots is performed as part of a first process that is executed independently of one or more processes executing the replicating of the write operations.

3. The method of claim 1 , wherein the plurality of snapshots are listed in the list in a chronological order from an earliest point in time corresponding to a snapshot to a latest point in time corresponding to a snapshot, and wherein the replicating of the plurality of snapshots includes:
replicating a first snapshot of the plurality of snapshots to a first replica snapshot on the second storage system, including, for each logical storage element of the first logical storage unit:
determining if one or more write operations received on the first storage system for the logical storage element have had data stored on the first storage system but not yet replicated to the second logical storage unit on the second storage system; and
if the one or more write operations for the logical storage element have had data stored on the first storage system but not yet replicated to the second logical storage unit, waiting for the data of the one or more write operations to be replicated to the second logical storage unit before replicating snapshot data of the logical storage element from the first storage system to the first replica snapshot on the second storage system.

4. The method of claim 3 , wherein the replicating of the first snapshot to the first replica snapshot includes, for each logical storage element of the first logical storage unit:
determining if any snapshot data for the logical storage element has been stored on the first storage system, but not yet replicated to the second storage system; and
if any snapshot data for the logical storage element has been stored on the first storage system, but not yet replicated to the second storage system, replicating the snapshot data from first storage system to the second storage system.

5. The method of claim 1 , wherein the plurality of snapshots are listed in the list in a chronological order from an earliest point in time corresponding to a snapshot to a latest point in time corresponding to a snapshot, and wherein the replicating of the plurality of snapshots includes:
after replicating a first snapshot of the plurality of snapshots, replicating a second snapshot of the plurality of snapshots to a second replica snapshot on the second storage system, including:
for each logical storage element of the first logical storage unit, determining if the logical storage element data has been modified between the first snapshot and the second snapshot; and
performing the remaining processing for replicating the second snapshot snapshots to the second replica snapshot on only the logical storage elements of the first logical storage unit that have been modified between the first snapshot and the second snapshot.

6. The method of claim 5 , further comprising, for each logical storage element of the first logical storage unit that has been modified between the first snapshot and the second snapshot:
determining if a value of the logical storage element for the second snapshot is a same value as a current value of the logical storage element on the first storage system; and
if the value of the logical storage element for the second snapshot is the same value as the current value of the logical storage element on the first storage system, updating metadata of the second replica snapshot for the logical storage element to reference the current value of the logical storage element on the second storage system.

7. The method of claim 5 , further comprising, for each logical storage element of the first logical storage unit that has been modified between the first snapshot and the second snapshot:
determining if a value of the logical storage element for the second snapshot is a same value as a current value of the logical storage element on the first storage system; and
if the value of the logical storage element for the second snapshot is not the same value as the current value of the logical storage element on the first storage system:
copying snapshot data of the logical storage element specified for the second snapshot from the first storage system to the second storage system; and
updating metadata of the second replica snapshot for the logical storage element to reference the copied snapshot data.

8. A system comprising:
a first storage system;
a second storage system;
a first logical storage unit, wherein the first storage system is configured to replicate data of the first logical storage unit to a second logical storage unit on the second storage system; and
executable logic that implements a method including:
recording a list of a plurality of snapshots of the first logical storage unit that were taken on the first storage system but not replicated to the second storage system because of a first period of time during which the replication of the first logical storage unit to the second logical storage unit is inactive; and
in response to the replication of the first logical storage unit to the second logical storage unit becoming active, accessing the list and replicating the plurality of snapshots of the list from the first storage system to replica snapshots on the second storage system,
wherein the replicating of the plurality of snapshots is performed concurrently to replicating write operations as part of the replication of the first logical storage unit to the second logical storage unit.

9. The system of claim 8 , wherein the replicating of the plurality of snapshots is performed as part of a first process that is executed independently of one or more processes executing the replicating of the write operations.

10. The system of claim 8 , wherein the plurality of snapshots are listed in the list in a chronological order from an earliest point in time corresponding to a snapshot to a latest point in time corresponding to a snapshot, and wherein the replicating of the plurality of snapshots includes:
replicating a first snapshot of the plurality of snapshots to a first replica snapshot on the second storage system, including, for each logical storage element of the first logical storage unit:
determining if one or more write operations received on the first storage system for the logical storage element have had data stored on the first storage system but not yet replicated to the second logical storage unit on the second storage system; and
if the one or more write operations for the logical storage element have had data s

Assignees

• Emc Ip Holding Co Llc

Inventors

• Bora Bhaskar
• Halstead Mark J
• Wilson Jeffrey

Classifications

• G06F3/065

  Replication mechanisms · CPC title

• G06F3/0619

  in relation to data integrity, e.g. data losses, bit errors · CPC title

• G06F3/067

  Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS] · CPC title

• G06F11/2097

  maintaining the standby controller/processing unit updated (initialisation or re-synchronisation thereof G06F11/1658 and subgroups) · CPC title

• G06F11/2094 Primary

  Redundant storage or storage space (G06F11/2056 takes precedence) · CPC title