Couchbase Server and Cross Datacenter Replication

Anil KumarTechnical Product Manager

XDCR: Cross Datacenter Replication

US DATA CENTER

EUROPE DATA CENTER

ASIA DATA CENTER

http://blog.groosy.com/wp-content/uploads/2011/10/internet-map.jpg

Cross Datacenter Replication – The basics

• Replicate your Couchbase data across clusters

• Clusters may be spread across geos

• Configured on a per-bucket basis

• Supports unidirectional and bidirectional operation

• Application can read and write from both clusters (active – active replication)

• Replication throughput scales out linearly

• Different from intra-cluster replication

Intra-cluster Replication

Cross Datacenter Replication (XDCR)

XDCR Architecture

33 2

Single node - Couchbase Write Operation with XDCR

Managed Cache

Dis

k Q

ueue

Disk

Replication Queue

App Server

Couchbase Server Node

Doc 1Doc 1

Doc 1

To other node

XDCR Engine

Doc 1

To other cluster

Internal Data Flow

1. Document written to managed cache

2. Document added to intra-cluster replication queue

3. Document added to disk queue

4. XDCR push replicates to other clusters

XDCR in actionCOUCHBASE SERVER CLUSTERNYC DATA CENTERACTIVE

Doc

Doc 2

SERVER 1

Doc 9

SERVER 2 SERVER 3

RAM

Doc Doc Doc

ACTIVE

Doc

Doc

Doc RAM

ACTIVE

Doc

Doc

DocRAM

DISK

Doc Doc Doc

DISK

Doc Doc Doc

DISK

COUCHBASE SERVER CLUSTERSF DATA CENTER

ACTIVE

Doc

Doc 2

SERVER 1

Doc 9

SERVER 2 SERVER 3

RAM

Doc Doc Doc

ACTIVE

Doc

Doc

Doc RAM

ACTIVE

Doc

Doc

DocRAM

DISK

Doc Doc Doc

DISK

Doc Doc Doc

DISK

Bucket-level XDCR

Bucket A

Bucket B

Bucket C

Cluster 1

Bucket A

Bucket B

Bucket C

Cluster 2

Continuous Reliable Replication

• All data mutations replicated to destination cluster

• Multiple streams round-robin across vBuckets in parallel (32 default)

• Automatic resume after network disruption

Cluster Topology Aware

• Automatically handles node addition and removal in source and destination clusters

Efficient• Couchbase Server de-duplicates writes to disk

­ With multiple updates to the same document only the last version is written to disk

­ Only this last change written to disk is passed to XDCR

• Document revisions are compared between clusters prior to transfer

Active-Active Conflict Resolution

• Couchbase Server provides strong consistency at the document level within a cluster

• XDCR provides eventual consistency across clusters

• If a document is mutated on both clusters, both clusters will pick the same “winner”

• In case of conflict, document with the most updates will be considered the “winner”

{ … } 33{ … }

Doc 1 on DC1Doc 1 on DC2

Winner

Configuration and Monitoring

STEP 1: Define Remote Cluster

STEP 2: Start Replication

Monitor Ongoing Replications

Detailed Replication Progress• Source Cluster

• Destination Cluster

XDCR Topologies and Use Case

Unidirectional

• Hot spare / Disaster Recovery

• Development/Testing copies

Bidirectional

• Multiple Active Masters

• Disaster Recovery

• Datacenter Locality

Chain

Data aggregation

Data propagation

XDCR in the Cloud

• Server Naming­ Optimal configuration using DNS name that resolves to internal address

for intra-cluster communication and public address for inter-cluster communication

• Security­ XDCR traffic is not encrypted, plan topology accordingly­ Consider 3rd party Amazon VPN solutions

Impact of XDCR on the cluster

Your clusters need to be sized for XDCR

• XDCR is CPU intensive ­ Configure the number of parallel streams based on your CPU capacity

• You are doubling your I/O usage­ I/O capacity needs to be sized correctly

• You will need more memory particularly for bidirectional XDCR ­ Memory capacity needs to be sized correctly

Q & A

Coming September 13

Featured speakers include:

http://www.couchbase.com/couchbase-sf-2013

Thank you

@ANILKUMAR1129ANIL@COUCHBASE.COM

Get Couchbase Server from http://www.couchbase.com/download