Clustering

http://www.redhat.com/cluster_suite/
take the demo with a grain of salt: I'm not showing a scenario where apache or mysql crash due to application error, but instead this is a “clean” test due to induced hardware failure.
- use the echo “c” > /proc/something (see kdump talk)

supports up to 16 nodes
does both application/server failover, and ip load balancing (load balancing is derived from Piranha)
doesn't do resource monitoring, can't distribute computational loads (for things like HPC)
service locking control done by fencing and STONITH
uses Distributed lock manager for shared resources
- shared resources can be:
  - NFS
  - SCSI and iSCSI
  - Fiber
  - CIFS
  - GFS2 (allows nodes direct concurrent access to shared resources, no client/server roles)

Nodes
- these are the hosts that will be part of a cluster
- nodes are configured to use a fence device
Fence Devices
- These provide the STONITH functionality, and prevent “split-brain” situations
Managed Resources
- These are the cluster's resources
- Failover domain
  - This defines the set of nodes for a particular service
- Resources
  - IP Address
  - Storage
  - Init script
- Services
  - The actual application that the cluster is running (service uses resources and failover domain)

easy enough to setup initialy, but there is testing needed before it's ready for production
- need some tests to see what happens when an application/server/services fails in the middle of an operation

With RHEL 6, Red Hat seems to be pushing Clustering as a more serious solution
- their documentation was recently updated and seems to be more organized and clearer
- RHEL is promoting RHEL 6 Clustering with Oracle as an alternative to Oracle RAC