Why High Availability Can’t Substitute Disaster Recovery

October 22, 2015 Disaster Recovery Blog, High Availability Blog Articles

High availability solutions make your data available; disaster recovery solutions make your data timeless.

High availability does not equal disaster recovery. While each solution provides essential features for business continuity and security, on their own they’re only half of the picture.


The Difference Between High Availability & Disaster Recovery

While many people confuse high availability (HA) and disaster recovery (DR) as interchangeable solutions, each really gives a very different result.

HA’s focus is business continuity. This involves replicating the data from your main production system to a secondary target, which you can switch to almost immediately in the event of a disaster. At the end of the day, HA keeps the most recent version of your business production available, in almost any scenario.

On the other hand, DR gives you the unique option to recover. Imagine that you’re being sued by a former employee. You know they’re making a false claim, and you have the e-mail to prove it – but that e-mail is buried 12 months back in someone’s trash folder that is now empty. HA solutions can’t give you the retention period you need. With DR solutions, your provider can go back in time and reobtain this e-mail, restoring it as if it was just sent yesterday.

Imagine another scenario: someone is cleaning up their desktop and accidentally deletes a critical file. High availability makes your data availablebut that’s not to say that this is the same data you want to be available. With HA solutions, this error will be replicated so that you have multiple copies of the same system, each lacking the file of interest. You can’t go back in time before the error occurred and pick up where you left off – only DR solutions can give you this kind of flexibility. The same is true of data corruption, whether it be on accident, by an unhappy employee, or from a malicious attack by a hacker.


Each Solution’s Forté

Backups are typically used for everything, from your personal desktop to entire servers. DR solutions give you the longest possible retention period, or the longest length of time in which you can restore a particular version of a file.

Just a few of the many situations DR can resolve are:

  • Data corruption
  • Total system failure
  • Accidental file deletion
  • Recovery of lost e-mails
  • Restoration to a previous version of production

Replication, or HA, is typically used for certain business-critical applications or servers that could affect other functioning if they crash. This doesn’t let you go back in time, but this does give you a recovery point objective (RPO) of seconds, running from the latest version of production. In the case of partial server failure, or only one application crashing, expertise in layer 2 communications can also allow for partial server failover.

Some key benefits of HA include:

  • Partial server failover
  • Enhanced business continuity
  • Virtually eliminated downtime
  • Some capabilities for restoration of recently lost data

The bottom line is that neither solution can substitute the other. With only one of the two in place, critical features – either downtime elimination or data security – are being neglected.


Long Story Short

HA brings your recovery point objective (RPO) down to seconds, but can’t go back in time to recover old data. DR takes longer to coordinate, but can obtain information from one of numerous backups of your system.

In today’s always-on environment, having both DR and HA is the only way to be sure that your business-critical functioning can be maintained nonstop, with the ability to access data from almost any point in time. Add them together, and it’s hard to imagine a scenario your data couldn’t stand up against.


To find out more about how these solutions apply specifically to your IT environment, contact us today at 317-707-3941.


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