Virtual Machine HA (VM HA) implements high availability at the hypervisor level by replicating and restarting full virtual machines, while Application HA implements high availability at the application level by replicating only application data and restarting the application. The two solutions do not offer the same level of high availability as explained in this article.
SafeKit offers a complete solution for application HA that solves hardware failures (20% of problems) including the complete failure of a computer room, software failures (40% of problems) including smooth upgrade server by server and human errors (40% of problems) thanks to simplicity of its administration.
Although there is an integration per application (restart scripts), the integration is simple and is made through application modules. Many examples of HA modules are given here.
VM HA solves only problems of hardware failures (20% of problems).
SafeKit offers a simple and economical solution to build virtual machines high availability on Hyper-V or virtual machines high availability on KVM with
The architecture does not require a shared disk or a replicated SAN if the two servers are in two remote computer rooms.
VM HA with the SafeKit Hyper-V or KVM module | Application HA with SafeKit application modules |
SafeKit with the Hyper-V module or the KVM module | Microsoft Hyper-V Cluster & VMware HA |
Note that the Hyper-V/SafeKit and KVM/SafeKit solutions are limited to replication and failover of 25 VMs.
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 | | |
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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