Reference

1. Install directory Structure

svn-multisite-plus
drwxr-xr-x 2 wandisco wandisco 4096 Dec  5 01:16 bin

        -rwxr-xr-x 1 wandisco wandisco 6258 Mar 13 18:34 common.sh
        -rwxr-xr-x 1 wandisco wandisco  552 Mar 13 18:34 multisite_enterprise_shutdown.sh
        -rwxr-xr-x 1 wandisco wandisco  595 Mar 13 18:34 multisite_enterprise_start.sh
        -rwxr-xr-x 1 wandisco wandisco  378 Mar 13 18:34 replicator_shutdown.sh
        -rwxr-xr-x 1 wandisco wandisco  400 Mar 13 18:34 replicator_start.sh
        -rwxr-xr-x 1 wandisco wandisco 5480 Mar 13 18:34 start_install.sh
        -rwxr-xr-x 1 wandisco wandisco 3689 Mar 13 18:34 start_upgrade.sh
        -rwxr-xr-x 1 wandisco wandisco  357 Mar 13 18:34 ui_shutdown.sh
        -rwxr-xr-x 1 wandisco wandisco  379 Mar 13 18:34 ui_start.sh
        -rwxr-xr-x 1 wandisco wandisco  524 Mar 13 18:34 wdog_rep.sh
        -rwxr-xr-x 1 wandisco wandisco  725 Mar 13 18:34 wdog_ui.sh

drwxrwxr-x 2 wandisco wandisco 4096 Dec  5 13:21 config
	
        -rw-rw-r-- 1 wandisco wandisco 5 Dec  5 13:53 setup.pid

-rw-rw-r-- 1 wandisco wandisco  256 Dec  5 13:56 license.key

drwxrwxr-x 2 wandisco wandisco 4096 Dec  5 14:20 local-ui
	-rw-rw-r-- 1 wandisco wandisco 1020 Dec  5 14:35 ui.properties

drwxrwxr-x 2 wandisco wandisco 4096 Dec  5 14:20 logs
        
        -rw-rw-r-- 1 wandisco wandisco 32647705 Dec  6 09:50 replicator.log.20121205-142035
	-rw-rw-r-- 1 wandisco wandisco   775889 Dec  6 15:00 replicator.log.20121206-101206
        -rw-r--r-- 1 wandisco wandisco  1185 Mar 14 09:40 start_install.20130314-094034
        -rw-r--r-- 1 wandisco wandisco 18606 Mar 14 10:14 ui.log.20130314-094038.1960
        -rw-r--r-- 1 wandisco wandisco  3506 Mar 15 11:50 ui.log.20130314-101437
        -rw-r--r-- 1 wandisco wandisco   809 Mar 14 10:14 wdog_rep.20130314-101436
        -rw-r--r-- 1 wandisco wandisco  1012 Mar 14 10:14 wdog_ui.20130314-094038
        -rw-r--r-- 1 wandisco wandisco   807 Mar 14 10:14 wdog_ui.20130314-101436        

drwxr-xr-x 8 wandisco wandisco 4096 Dec  5 14:20 replicator


        drwxr-xr-x 2 wandisco wandisco    4096 Mar 15 09:48 content
        drwxr-xr-x 5 wandisco wandisco    4096 Mar 14 10:14 database
        drwxr-xr-x 3 wandisco wandisco    4096 Mar 13 18:34 docs
        drwxr-xr-x 6 wandisco wandisco   4096 Mar 13 18:34 lib
        drwxr-xr-x 2 wandisco wandisco    4096 Mar 13 18:34 licenses
        drwxr-xr-x 4 wandisco wandisco    4096 Mar 15 14:24 logs
        -rw-r--r-- 1 wandisco wandisco 1079544 Mar 13 18:34 ms5-replicator.jar
        drwxr-xr-x 2 wandisco wandisco    4096 Mar 14 09:40 properties
        
        
        -rw-r--r-- 1 wandisco wandisco 1079560 Mar 13 18:34 upgrade.jar
        -rw-r--r-- 1 wandisco wandisco      26 Mar 13 18:34 VERSION

	drwxrwxr-x 2 wandisco wandisco 4096 Dec  5 13:21 systemdb
	drwxr-xr-x 3 wandisco wandisco 4096 Dec  5 01:16 ui

2. Properties Files

The following files store application settings and constants that may need to be referenced during troubleshooting. However, you shouldn't make any changes to these files without consulting WANdisco's support team.

<INSTALL-DIR>/svn-multisite-plus/replicator/properties/application.properties

file contains settings for the replicator and affects how MultiSite performs. [view sample]

<INSTALL-DIR>/svn-multisite-plus/replicator/properties/logger.properties

handles properties that apply to how logging is handled. [view sample]

<INSTALL-DIR>/svn-multisite-plus/replicator/properties/replicator-api-authorization.properties

handles properties that are used for managing remote access through the API. [view sample]

<INSTALL-DIR>/svn-multisite-plus/local-ui/ui.properties

contains settings concerning the graphical user interface such as widget settings and timeout values. [view sample]

3. Replication Strategy

Subversion MultiSite provides a toolset for replicating Subversion repository data in a manner that can maximise performance and efficiency whilst minimising network and hardware resources requirements. The following examples provide you with a starting point for deciding on the best means to enable replication across your development sites.

3.1 Replication Model

In contrast with earlier replication products, Subversion MultiSite: Enterprise Edition is no longer based upon a network proxy that handles file replication between replica. Now, replication is handled at the filesystem level, via FSFS.

Subversion MultiSite Enterprise edition differs from earlier WANdisco replication products on a number of levels.

Limitations of the old model

• The replicator sits in front of Apache
• All reads have to pass through the replicator
• Requires some functionality to be added so that certain operations can be performed prior to scheduling a transaction for replication
• Authentication against external data stores
• Hooks firing

Subversion MultiSite Enterprise edition differs from earlier versions in that it replicates at the file system level.

3.1.1 Per-Repository Replication

Subversion MultiSite is able to replicate on a per-repository basis. This way each site can host different sets of repositories and replicate repositories this means that you can have different repositories replicate as part of different replication groups.

3.1.2 Dynamic Membership Evolution

No need for a synchronized stop - Subversion MultiSite Enterprise allows replication groups to change their membership on-the-fly.

A repository can only replicate to a single replication group at any one time, although it is possible to move between replication groups as required - this can now be done on-the-fly, nodes can be added or deleted without the need to pause all replication (with a synchronized stop)

Subversion MultiSite Enterprise offers a great deal of flexibility in how repository data is replicated. Before you get started it's a good idea to map out which repositories at which locations you want to replicate.

3.2 Creating resilient Replication Groups

SVN MultiSite Plus is able to maintain Subversion repository replication (and availability) even after the loss of nodes from a replication group. However, there are some configuration rules that are worth considering:

Rule 1: Understand Learners and Acceptors

The unique Active-Active replication technology used by SVN MultiSite Plus is an evolution of the Paxos algorithm, as such we use some Paxos concepts which are useful to understand:

• Learners:
  Learners are the nodes that are involved in the actual replication of Subversion repository data. When changes are made on the local repository copy these nodes raise a proposal for the changes to be made on all the other copies.

  Learner Nodes are required for the actual storage and replication of repository data. You need a learner node at any location where Subversion users are working or where you wish to store hot-backups of repositories
  
  Types of Nodes that are learners: Active, Passive




• Acceptors:
  All changes being made on each repository in exactly the same order is a crucial requirement for maintaining syncronization. Acceptors are nodes that take part in the vote for the order in which proposals are played out.

  Acceptor Nodes are required for keeping replication going. You need enough Acceptors to ensure that agreement over proposal ordering can always be met, even accounting for possible node loss. For configurations where there are a an even number of voters it is possible that voting could become tied. For this reason it is possible to make a voter node into a tie-breaker which has slightly more voting power so that it can outvote another single voter node.
  
  Types of nodes that are Acceptors: Voter Only
  Nodes that are both an Acceptor and Learner: Active Voter, Passive Voter

Rule 2: Replication groups should have a minimum membership of three learner nodes

Two-node replication groups are not fault tolerant, you should strive to replicate according to the following guideline:

• The number of learner nodes required to survive population loss of N nodes = 2N+1
  where N is your number of nodes.

  So in order to survive the loss of a single node you need to have a minium of 2x1+1= 3 nodes
  In order to keep on replicating after losing a second node you need 5 nodes.