WANdisco's Subversion MultiSite

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Subversion MultiSite (http://www.wandisco.com) leverages WANdisco's unique replication technology to immediately synchronize Subversion repositories connected over a wide area network (WAN). Users at …

Subversion MultiSite (http://www.wandisco.com) leverages WANdisco's unique replication technology to immediately synchronize Subversion repositories connected over a wide area network (WAN). Users at every location experience local area network (LAN) speed performance for both read and write operations. Subversion MultiSite also provides continuous hot backup and self-healing capabilities that automate disaster recovery, so that downtime is virtually eliminated.

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  • 1.  
  • 2.
    • Peer-to-peer architecture with no single point of failure.
    • Not master-slave or multi-master .
      • Repositories at every site are fully readable and writeable.
    • Subversion repositories connected over a WAN synchronize automatically with each write operation.
    • Developers at all locations experience LAN speed performance over a WAN for both read and write operations.
    • Built-in hot backup and automated disaster recovery features make third party solutions completely unnecessary.
    • Transparent implementation doesn’t change Subversion’s behavior, so there’s no retraining.
    Key Features
  • 3.
    • Replicator implemented as a transparent network proxy at each site.
      • Normally installed on the same server as Apache at each location.
      • Listens on same port clients use to connect to Subversion:
        • Port 80 for HTTP.
        • Port 443 for HTTPS.
      • No client configuration changes.
      • No changes to Subversion server.
    Architecture
  • 4.
    • LAN-speed performance over a WAN results
    • from a combination of Subversion MultiSite’s:
    • Active-active replication capability:
      • Subversion servers become active nodes on a network.
      • Each node works cooperatively with its peers to agree on transaction ordering.
      • Each node’s repository becomes an exact replica of every other.
    • Quorum Configuration
      • Only a quorum of nodes have to agree on transaction ordering.
      • Quorum based on distribution of users/activity across sites for best performance .
    • Network Architecture
      • Minimizes number of WAN roundtrips and bandwidth usage.
    Architecture
  • 5.
    • How it works:
    • The replicator generates a proposal (header) for each write at its location and sends it to its peers.
      • The proposal contains a globally unique transaction id and other data used to determine if conflicts exist.
      • The proposal’s unique transaction id is used at every location to guarantee consistent transaction order.
    • Users experience LAN speed performance.
      • Once agreement is received from a quorum of nodes, the write goes forward at the site where it originated.
      • No waiting for other sites to complete the write.
      • Agreement takes less than half a second between US and India over a typical E-1 line.
      • All reads are local and generate no WAN traffic.
    Active-Active Replication
  • 6. Quorum Configuration
    • How it works:
    • Quorum configuration options:
      • Majority - Only 51% of nodes required to respond to proposal.
        • Distinguished Node – node used as tie-breaker with an even number of nodes
      • Singleton - The Distinguished Node is the quorum .
        • Ideal if one site has many more users and activity than others.
          • Superior performance at the quorum site.
        • Responses from remote nodes are not required at the Distinguished node
          • No WAN traffic generated for agreement process .
          • Writes get sent to other nodes after agreement process completes at distinguished node.
      • Unanimous - Responses required from all nodes
    • Follow-the-sun quorum rotation
        • Optimizes performance for each region’s normal working hours.
  • 7. Network Optimization
    • How it works:
    • Reduces network traffic and bandwidth usage and costs
    • All reads are local and generate no WAN traffic
    • Streaming on Persistent connection between servers
      • Connection pooling used for multiplexing
      • TCP 3-Way Handshake Eliminated
    • Uses WANdisco’s own protocol over the WAN
      • Eliminates normal Subversion chattiness over the WAN
      • WAN roundtrip times are significantly reduced
    • Overcomes WAN performance issues with HTTP WebDAV Protocol
      • Entire commit with multiple files can be sent over one connection.
      • Other solutions open and close connections for each file.
  • 8. Demo
  • 9. Built-in Backup and Recovery
    • Active-Active replication delivers continuous hot backup by default.
    • Subversion MultiSite leverages this to provide automated recovery.
      • Catch up from any other live node on restart after a network outage or server crash.
      • Maintains a database-like redo log/pending transaction journal for recovery.
      • Split brain is impossible.
    • Users can failover to another site’s Subversion server while theirs is down and continue working.
    • Makes full 24x7 operation possible in a globally distributed environment.
      • Servers can be taken offline for maintenance without disrupting user access.
    • Third party disk mirroring solutions are completely unnecessary.
  • 10.
    • Server Versions Supported
      • Subversion server versions 1.3 and above are supported.
    • Backend Support:
      • FSFS and Berkeley DB are supported.
    • Supported Clients
      • Subversion command line, SmartSVN, RapidSVN, TortoiseSVN, Subclipse, and any HTTP client that works with Subversion.
    • System Requirements
      • WANdisco for Subversion will run in any J2SE 1.5 or above compliant Java runtime environment. A minimum of 64 MB of RAM and 450MHz CPU is recommended for the server
    System Requirements
  • 11.
    • Unique technology allows distributed development teams to work as one at LAN-speed over a WAN, instead of working in silos.
    • Dramatically reduces development time and cost.
    • Peer-to-peer architecture with no single point of failure.
    • All servers can be monitored and administered from a single location.
    • Built-in continuous hot backup and self-healing capabilities eliminate risk in a disaster recovery scenario.
    • Makes full 24X7 operation possible in a globally distributed environment.
    • Transparent implementation eliminates retraining.
    • Most cost effective multi-site solution available.
    Summary