The SafeKit software provides a simple active active cluster with real-time replication on Windows or Linux. Applications are running on two servers in mutual failover. Each server is backup of the other server. And each application works on its own replicated file directories.
If one server fails in an active active cluster, all applications will be active on the same server. After restart of the failed server, applications will return to run on their default primary server.
The SafeKit active active cluster is simply configured by deploying two mirror modules with real-time replication. Each mirror module contains its own configuration of virtual IP address, real-time replicated directories and restart scripts.
Note that:
The Hyper-V replication automatic failover and load balancing solution is an example of an active-active cluster with N mirror modules replicating N virtual machines between two physical servers. In this configuration, a mirror module replicates a full virtual machine and restarts the virtual machine in case of failure. There is no virtual IP in such a module because restarting a VM on a server makes automatically the IP failover of the VM. And an application is installed in one single VM in this architecture.
As presented in the Hyper-V cluster demonstration, an active active cluster can implement real-time data replication for directories inside the operating system disk. Note that replicating data inside the system disk is possible with byte-level file replication and impossible with block-level disk replication.
Another way to implement an active active cluster with SafeKit is the network load balancing cluster described here.
Evidian SafeKit mirror cluster with real-time file replication and failover | ||
All clustering features | |
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Synchronous replication | |
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Fully automated failback procedure | |
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Replication of any type of data | |
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File replication vs disk replication | |
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File replication vs shared disk | |
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Remote sites and virtual IP address | |
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Quorum | |
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Active/active cluster | |
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Uniform high availability solution | |
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Evidian SafeKit farm cluster with load balancing and failover | ||
No load balancer or dedicated proxy servers or special multicast Ethernet address | |
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All clustering features | |
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Remote sites and virtual IP address | |
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Uniform high availability solution | |
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High availability architectures comparison | ||
Feature | SafeKit cluster | Other clusters |
Software clustering vs hardware clustering | | |
Shared nothing vs a shared disk cluster | | |
Application High Availability vs Full Virtual Machine High Availability | Smooth upgrade of application and OS possible server by server (version N and N+1 can coexist) | Smooth upgrade not possible |
High availability vs fault tolerance | Software failure with restart in another OS environment. Smooth upgrade of application and OS possible server by server (version N and N+1 can coexist) | Software exception on both servers at the same time. Smooth upgrade not possible |
Synchronous replication vs asynchronous replication | | |
Byte-level file replication vs block-level disk replication | | |
Heartbeat, failover and quorum to avoid 2 master nodes | | |
Virtual IP address primary/secondary, network load balancing, failover | | |
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