In this short series of blog posts, we’ll be looking at five important considerations you need to make when choosing a virtual server. It may seem that all virtual servers, or cloud servers, are similar, but like everything technical, the devil is in the detail.
Danger 1: The danger of hardware failure
One of the benefits of virtualisation should be an improvement of service availability, so it’s important that the topology of the cluster is well thought out, such that a failure of a major central component such as a network switch, or even just the physical node (server) that your virtual server is running on, doesn’t cause your virtual server to go offline.
Use Centralied SAN Storage
The best solution uses centralised SAN storage, so that if the physical node (server) you’re running on fails, your virtual server will automatically re-start on a spare node.
An added benefit of this is that your hosting service can take nodes out of service for maintenance without affecting your virtual server. That means you’re truly available for the maximum amount of time possible.
Look for an option of fast disks (i.e. 15,000rpm SAS disks) to keep the I/O throughput of your virtual server tip-top.
Use Hardware Resilience
Nodes should be dual-uplinked through two switches, to both the frontend (i.e. the internet) and also the backend (i.e. to the storage) such that the failure of a network switch or uplink cable (or just someone accidentally un-plugging it) does not stop your virtual server from running, or being accessible.
The centralised SAN storage should be built with resilient/failover power supplies and controllers, such that the failure of any component within the SAN does not take offline any virtual server.
A decent service provider will offer the option of offsite backup space to be mounted to your virtual server to give you a self-standing off-site copy of your important data.
Daniel Keighron-Foster, Managing Director
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