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Replication overview

InfiniBox replication is a complete feature set for data recovery, remote copy and high availability of the customer's data between Infinibox systems.

Infinibox Async Replication is a snapshot-based solution that protects the data by replicating it to a remote site without adding latency to the host I/Os. The replication of the data is done asynchronously with a minimal 4 secs RPO (Recovery Point Objective).

Infinibox Sync Replication is a synchronous replication solution that protects the data with zero RPO. Every write to the local system is immediately written to a copy of the dataset on the remote system before returning to the host.

Infinibox Active-Active Replication is a synchronous replication solution that protects the data with zero RPO and zero RTO (Recovery Time Objective). The data of the replicated datasets can be accessed by the host on both systems at the same time.

InfiniBox replication uses standard Ethernet networking, and is optimized to improve replication performance for both close-proximity systems as well as long-range high-latency networks:

  • The use of standard TCP algorithms allow InfiniBox to maintain high network link utilization while maintaining fairness
  • InfiniBox custom flow control algorithm takes into consideration the load on the source system, load on the target system, and memory consumption on both sides to tune resource utilization
  • InfiniBox provides the ability to limit replication network utilization, allowing users to manually control their network load

InfiniBox version requirements for replication

Volumes, consistency groups, and filesystems can be replicated across multiple InfiniBox systems that either run the same major version or else are one major version apart. The major version is the first term of the InfiniBox version number. For example, you can replicate entities between InfiniBox versions 5.0.3 and 5.5.40 (same major version), and between InfiniBox versions 5.0.3 and 6.0.20 (one major version apart).
Replication is not supported across systems that are more than one major version apart. For example, versions 
4.0.60 and 6.0.20.

Async replication overview

The InfiniBox Async Replication is a snapshot-based solution that allows the users to protect their data by replicating it to a remote site without adding latency to the host I/Os.

The async replication allows overcoming large geographic distances by:

  • Sending the I/O to the remote site after it was already acknowledged by the host
  • Allowing the user to define the interval between the snapshots that are sent to the remote site
  • Supporting a minimal 4 secs RPO (Recovery Point Objective) if the link quality requirements between the sites are fulfilled.

Async replication topology diagram

With InfiniBox async replication, when the host sends a write request to a dataset on the source system, the write is acknowledged to the host immediately and then replicated to the target system.

The following diagram shows the async replication data flow:

  1. The host sends a write I/O request to the source InfiniBox
  2. The source InfiniBox acknowledges the write I/O to the host
  3. The source InfiniBox replicates the data to the target InfiniBox
  4. The target InfiniBox acknowledges the replication to the source InfiniBox

Sync replication overview

The InfiniBox Sync replication allows the user to protect the data synchronously, sending the I/O to the remote site before acknowledging the host.

The synchronous replication will have an impact on the latency of the write I/O to the host since the acknowledge to the host will be sent only after the data was written in both sites.

Read I/O will be served locally from the source system so no latency will be added.

The InfiniBox synchronous replication solution depends on the quality of the link between the sites. If the link requirements are not fulfilled, the InfiniBox will move the replica to an internal asynchronous mode until the link requirements are met.

Synchronous replication topology diagram

With InfiniBox synchronous replication, when the host sends a write request to a dataset on the source system, the write is replicated to a dataset on the target system prior to any acknowledge to the host. Only after the target system has acknowledged the write to the source system, the source system acknowledges the write to the host.

The following diagram shows the synchronous replication data flow:

  1. The host sends a write I/O request to the source InfiniBox
  2. The source InfiniBox synchronously replicates the data to the target InfiniBox
  3. The target InfiniBox acknowledges the replication to the source InfiniBox
  4. The source InfiniBox acknowledges the write I/O to the host

Changing the replication type between Sync and Async

The replication type of a replica is determined by the user when the replica is created and can be changed anytime later on (except when the replica undergoes Initialization).

  • When the replication type is changed from Synchronous to Asynchronous the user has to specify the Interval and RPO
  • When the replication type is changed from Asynchronous to Synchronous:
    • The Sync state is set to Sync In Progress until the replica is Synchronized

Active-Active replication overview

Infinibox Active-Active replication is the perfect solution for keeping business continuity for clustered applications.

Active-Active replication is a symmetric synchronous replication solution that allows the application to run with no down time and immediate recovery in case of failures.

Helps spreading the app workload across data centers with minimal management and even provide a solution to non-disruptive data mobility on the storage level.

Infinibox Active-Active solution basics

  1. Peer-to-Peer replication - Both sides of the replication are equal. Both are writable and readable by the hosts.
  2. Low latency sync replication - Data is transferred only once over the link, the latency is the same on both systems.

  3. Automatic failover and failback - Zero RPO and Zero RTO - The system automatically detects failures. When problem is resolved, automatic failback is performed.

  4. Highest level of protection and HA - Two levels of protection: Witness and “Preferred system” definition for a replica.

I/O with Active-Active replication

  • Active-Active replicated volumes are two separate volumes with the same serial ID.
  • Hosts that are mapped to these volumes will see them as the same entity with multiple path to it.
  • The volumes are available for read and writes on both systems when the reads are served locally and the writes are replicated to the remote system before sending the acknowledgement to the host. 
  • Write latency is the same on both systems since we make sure that the data is transferred only once over the link.
  • In case of a link failure between the systems, only one system will continue to serve I/O's.
  • The solution is based on ALUA (Asymmetric LUN access)  
  • Infinibox has two mechanism to handle failures for active-active replica: Witness and Preferred system definition

For more info about Infinibox Active-Active solution see Active-Active replication.

Mobility replication overview

InfiniBox mobility replication enables non-disruptive workloads movement between InfiniBox systems without any downtime. (Online Data Mobility)

  • Mobility replicas behavior and functionalities are identical to an Active-Active replica.

Mobility replicas are used during an Online Data Mobility process, which is initiated and managed from within the hosts using Host PowerTools.

  • InfiniBox GUI or InfiniShell cannot manage online data mobility, however allow to query for the Mobility replicas status. 
  • For more information about the Online Data Mobility process refer to the Host PowerTools documentation.
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Last edited: 2021-12-11 18:51:13 UTC

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