Towards Zero Downtime

Every aspect of business requires a different level of data protection and availability. Organizations with basic business needs for data protection and availability can benefit from technologies such as RAID and tape backup systems. On contrary, critical business needs require significant data protection and high availability which requires considerable planning, coordination, testing and capital. Simply spending money on independent point solutions is a poor choice since they do not merge the technologies and processes together.

High Availability

The term high availability implies a high level of reliability, redundancy and fault-tolerance to and at the source of information. It is argued that it is possible to achieve high availability with poor reliability, this notion fails to consider redundancy as a critical component- without redundancy you do not have high availability. It is important to consider operating procedures also have a significant impact on service availability. To avoid service outages, one must carefully consider service availability for all operating procedures.

Table 2:1 reflects the standard metrics used by the industry for system availability. As shown a Class 1 system operates at 90% or one 9 of availability and allows up to 50,000 minutes per year in downtime. A Class 5 system operates at 99.999 or five 9’s availability and allows up to 5 minutes per year in downtime. Many of today’s organizations strive to achieve "3 9s" availability (99.9 percent), which means that there can be only approximately 8 hours and 45 minutes of unplanned downtime a year. Communication companies such as AT&T in the United States typically strive to achieve "5 9s" or 99.999 percent uptime which means there can be only approximately 5 minutes of unplanned downtime a year.

Each progressive tier within the High Availability table implies higher availability, complexity, redundancy and cost. If monetary losses associated with an unplanned outage are unacceptable, solutions in the higher HA Tier are leveraged. Although any company can strive for additional uptime for its environment, significant incremental capital investment is required to achieve extra "9s." To better illustrate the High Availability Metrics, we need to evaluate the specific characteristics of HA tiers. We have provided examples that illustrate Managed systems that have a goal of achieving two “9”s to High Availability systems which strive for five “9”s.

High Availability Tier

This tier includes all the benefits of the other tiers and eliminates all single points of failure. This tier achieves the highest network, storage and server availability and provides 99.999% availability. Redundant servers are clustered together with either automatic load-balancing capability or automatic fail-over capability. The servers have redundant connections to different switches within the IP network, have redundant connections to the high-availability Storage Area Network (SAN), use a standard hardware and software platform, and are housed in an environmentally controlled computer room. All devices from the core routers to the disk drives have appropriate hardware and software maintenance and are powered by UPS equipment. The UPS equipment feeds into an emergency generator. All components of the infrastructure participate in a comprehensive enterprise-class management and monitoring system.

The server and storage system undergoes periodic testing for automatic failover assurance. A second datacenter acting as a warm datacenter provides Disaster Tolerance protection against a datacenter failure. Backup sets of data are available at the second data center through real time software or hardware data replication. Disaster Tolerance implies resumption of services and data within an hour.

The main characteristics of this tier include defined Sla’s, change control, high end server and storage availability, clustered servers, hardware load balancers, premium monitoring and alerting, redundant wan links, redundant firewall infrastructures, UPS, Backup Generator, common standard software and hardware platforms. In addition, proficient technical support is a vital characteristic of this tier. This tier strives to achieve 99.999% availability.