HA storage (high-availability storage)

Contributor(s): Sarah Wilson

High-availability storage (HA storage) is a storage system that is continuously operational or provides at least 99% uptime.

Redundancy is a key feature of HA storage, as it allows data to be kept in more than one place and eliminates a single points of failure (SPOF). HA storage systems are often used in virtual server environments as a security feature to protect critical virtual machines.

HA storage arrays require at least two controllers in case one is lost. For disaster recovery, HA storage requires a secondary storage system to hold critical data and applications the business needs if its primary storage system goes offline. This is often done by replicating data to another storage system at another site.

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See also: high-availability, five nines


This was last updated in November 2013

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I'm surprised to see the 99% number - that allows for three down days a year! 

When I was the insurance company, HA included heartbeat (management was notified if the system was down for more than 15 seconds) and automatic failover (so that 15 seconds was rare.)

My guess at HA would be more like 99.9 and above - 8 business hours a year.
Hi, Matt--

I agree--99% doesn't seem particularly aggressive, especially considering that some storage vendors tout five 9s for gear that's not even necessarily considered HA.