There are two kinds of high availability:

1. process high availability
2. data high availability

IBM WAS ND V6 processes include...

• Deployment manager
• Node agent
• WAS appservers
• HTTP server
• Load Balancer
• Database server
• Firewall
• LDAP server
• WebSphere MQ
• Networked file system (NFS, AFS, ...)
• Operating system

Even if you make all of these processes highly available, the WebSphere system might still fail due to data availability.

Data stored includes...

• Application data for the appservers.
• Administrative repository for WAS admin servers (XML files).
• Persistent session data for WebSphere HTTP sessions (If not using memory-to-memory session replication)
• Persistent data for Entity EJBs.
• The default messaging provider data store.
• WebSphere security data for the LDAP servers.
• Transaction log files and other log files.
• WebSphere system and application binaries.
• HTML and image files.

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