Shared nothing cluster vs shared disk cluster is an important point to consider when choosing a cluster solution. The deployment of a shared nothing cluster as implemented by SafeKit is much more simple than a shared disk cluster.
Simplicity of a shared nothing vs a shared disk cluster | ||
| Architecture | Shared nothing cluster
| Shared disk cluster
|
| Product | SafeKit on Windows Linux | Clustering toolkit for shared disk |
| Extra hardware | No - Use internal disks of servers | Yes - Extra cost with a shared bay of disks |
| Application data organization | 0 impact on application data organization with SafeKit. Just define directories to replicate in real-time. Even directories inside the system disk can be replicated. | Impact on application data organization. All data to recover must be localized in a special shared disk. Data in the system disk cannot be replicated. |
| Complexity of deployment | No - install a software on 2 servers | Yes - require specific IT skills to configure OS and shared disk |
| Failover | Just restart the application on the second server | Switch the shared disk. Remount the file system. Pass the recovery procedure on the file system. And then restart the application |
| Disaster revovery | Just put the 2 servers in 2 remotes sites connected by an extended LAN. Video of disaster recovery with a software SAN | Extra cost with a second bay of disks.New specific IT skills to configure mirroring of bays across a SAN. |
| Quorum and split brain | No data corruption in case of network isolation between the two servers (split brain). Cluster quorum video : no quorum server and no quorum disk | Require a special quorum disk or a third quorum server to avoid data corruption on split brain |
| Suited for | Software editors which want to add a simple high availabity to their application | Enterprise with IT skills and large database applications |
Here are some examples of mirror application modules:
Here are some examples of farm application modules:
More information on shared nothing clusters implemented by the SafeKit software on Windows and Linux here.
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