High Availability, and a lot... (work in progress)

High Availability
As more and more mission-critical applications move on the Internet, providing highly available services becomes increasingly important. One of the advantages of a clustered system is that it has hardware and software redundancy, because the cluster system consists of a number of independent nodes, and each node runs a copy of operating system and application software. High availability can be achieved by detecting node or daemon failures and reconfiguring the system appropriately, so that the workload can be taken over by the remaining nodes in the cluster.

pizzaman: "There are so many possible scenarios for doing HA stuff, hope that I'll be able to play with more of them soon."


Edit: Aug 16, 2006:

During this 3 days holiday, I've read through a lot and found many interesting solutions including:

• LVS itself (of course)
• Linux-HA
  
• pound
• pen
• HAProxy

Several nice articles:

• How to setup HA-LB apache cluster (using LVS)
• How to setup HA NFS server with DRBD
• HA NFS from linux-ha, including lock test results (however, the article is quite old and those problem should be solved by now)
  
• How to aggregate apache log files from several nodes
• NFS and LVM: We will need to work with shared NFS resource in our cluster
  
• RHEL4 NFS reference
  
• DRBD itself, so-called network RAID-1 data replicator(?)
  
• RedHat cluster suite + GFS

I later stumbled upon:

• Kevin Minnick's comments on these solutions (although I think pound doesn't provide HA on its own). Kevin touches upon perlbal, a good perl-based RP and load balancer that I've never heard of until now. Got to have a look later.
• At danga, I saw its DFS called MogileFS. Looks cool, altought it lacks POSIX compliance that I need.