Shared nothing cluster vs shared disk cluster

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.

Comparison table: shared nothing cluster vs shared disk cluster

Simplicity of a shared nothing vs a shared disk cluster


Shared nothing cluster

Shared nothing cluster

Shared disk cluster

Shared disk cluster

ProductSafeKit on Windows LinuxClustering toolkit for shared disk
Extra hardwareNo - Use internal disks of serversYes - Extra cost with a shared bay of disks
Application data organization0 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 deploymentNo - install a software on 2 serversYes - require specific IT skills to configure OS and shared disk
FailoverJust restart the application on the second serverSwitch the shared disk.
Remount the file system.
Pass the recovery procedure on the file system.
And then restart the application
Disaster revoveryJust 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 brainNo 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 forSoftware editors which want to add a simple high availabity to their applicationEnterprise with IT skills and large database applications

Examples of shared nothing cluster configurations with SafeKit and without shared disk

Here are some examples of mirror application modules:

Here are some examples of farm application modules:

Video comparing a shared disk cluster and a shared nothing cluster when considering disaster recovery

More information on shared nothing clusters implemented by the SafeKit software on Windows and Linux here.

More comparisons to understand how to achieve simplicity in high availability


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