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Network World - As recently as five years ago, business continuity and disaster-recovery topics would make IT executives in small to midsize enterprises grumble that neither was affordable. Now companies of all sizes are realizing they can have both using virtualization technology.
First, let's clarify the difference between business continuity and disaster recovery: Disaster recovery is about re-establishing IT services in the face of large-scale hardware failure or sabotage, facilities failure and/or regional natural disaster. Disaster-recovery capabilities are measured by the amount of time it takes to re-establish services and the amount of data loss. Business continuity is the ability to continue operations with little or no downtime in some of these scenarios.
Affordable shared storage was the first big step forward for disaster recovery for small to midsize enterprises (SMEs). When data is stored on disks inside a server, it is only as reliable and expandable as those servers: if a motherboard fails, your data is inaccessible, even though the disks may be fine. Storage-area network (SAN) and network-attached storage (NAS) devices pool the storage out of the server, increasing reliability, flexibility and ease of management.
Snapshots and replication, features of the latest generation of these devices, are at the heart of most effective disaster-recovery strategies. Snapshots capture the state of a storage system at a point in time, and replication is used to copy the state of one storage system to another. In conjunction with server imaging software, these snapshot and replication tools allow you to get back up and running on replacement hardware.
Yet there are still two key challenges: getting server hardware on short notice is not always easy, and even with the most recent imaging tools, you probably need the same hardware, which may no longer be available. Matched hardware sitting at a disaster-recovery site solves both these problems, but in most cases is not an affordable option.
Server virtualization has changed the rules. For one, it improves on imaging software. Virtual machines are fully encapsulated as files and then a thin layer of software -- a hypervisor -- allows these machines to be restarted on on any hardware. This removes the hardware dependence and makes it possible to use fewer disaster-recovery physical servers to support production systems -- allowing more organizations to afford the appropriate spare physical host(s). In fact, often the spare physical hosts have been freed up at the primary site with the consolidation made possible by server virtualization.
Virtual machine management and site recovery tools provide the interface to instruct the virtual machines to move to the off-site
location, where they are restarted in minutes or hours rather than days or weeks that were necessary previously.
With virtualization, you create a more resilient production architecture -- servers are easily moved among physical hosts, shared storage solutions provide enterprise class features with five-nines availability, snapshots provide multiple point in time recovery points -- meaning there will be fewer situations when utilizing the disaster-recovery strategy will be necessary. Yet, when it is necessary, SMEs can now avoid the costly downtime that can be so damaging for a business.