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.

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