Adding 9s to uptime can add up
The technology used for disaster recovery and business continuity service plans differs dramatically depending on the percentage of uptime that must be guaranteed.
A two-9s guarantee (99 percent uptime), for example, would allow for a couple of days of downtime per year. Although this would be acceptable for low-priority corporate applications, few transaction-heavy applications can withstand this much downtime. To guarantee 99 percent uptime, an IT manager could get by using simple tape backup without having the added expense of warm standby servers.
Boosting uptime to the three-9s level (99.9 percent uptime) would reduce acceptable downtime to a couple of hours a year. Disaster recovery providers are typically vendor-neutral, which should eliminate worries about losing the initial investments in backup systems.
But depending on the amount of data being protected, a tape-based recovery system along with standby servers might not be enough. For three-9s systems, more likely than not, off-site redundant servers will be required; these servers should run data mirroring software to ensure that, in the event of a disaster, the backup servers will be able to restore services.
Moving up to the five-9s range and beyond, distributed processing with load balancing becomes almost mandatory to meet uptime requirements. In this case, it would be common to see high-speed network connections running through powerful routers from companies such as Juniper Networks.
Before deciding on a disaster recovery and business continuity plan, make sure you know how much uptime your business really needs, because adding 9s can be an expensive proposition.
