Configuring a Disaster Recovery Host

Alteeve Wiki :: How To :: Configuring a Disaster Recovery Host

A Disaster Recovery host, aka "DR Host", is a physical server that is installed in a physically different location from the production Anvil! cluster.

The purpose of the DR host is to provide a fall-back location to run servers should the production cluster suffer a catastrophic failure. Consider failure scenarios like;

• Accidental fire suppression discharge
• Transformer failure feeding the data-center
• Localized fire in the cluster location

In such scenarios, the facility might still be perfectly able to function, but all cluster equipment is damaged or destroyed.

The DR host is often installed in an opposite corner of the facility, in another building on campus, or in an entirely different city. Where ever it happens to be, the DR host can be pressed into service!

Storage replication to the DR is streaming and ordered, but it is not synchronous. This way, the latency of the remote connection does not impact day to day performance, but the data being replicated to the DR host is ordered, even across multiple virtual disks. As such, the DR host may be allowed to fall a few seconds behind production, but the data will be contiguous.

What this means is that your servers will boot on the DR host, file system journals will replay, database write-ahead logs will work, and your applications will start, no different than if a machine had simply rebooted

The time to get the DR site online is measured in minutes. Far faster than recovering from even onsite backups with standby hardware!

DR Host Hardware Considerations

In an ideal configuration, there would be a dedicate DR host to match the hardware of each Anvil! node. In such a setup, a full fail-over to the DR site would be possible without any loss in performance.

For those with stricter budgets, a DR host's hardware can be sized such that a subset of core production servers are protected only.

Another possible configuration is to have one (or a few) much larger machines that each can provide DR hosting to 2 or more production nodes. Of course, the performance in such a configuration may be impacted. It is strongly advised to test that performance will be acceptable prior to deployment.

Connecting a DR Host to an Anvil Node

 

Any questions, feedback, advice, complaints or meanderings are welcome.
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