Issue link: http://cp.revolio.com/i/288390
www.datacenterjournal.com 14 | THE DATA CENTER JOURNAL GRANULAR AVAILABILITY Traditionally, a data center might be ranked as Tier I, Tier II, Tier III or Tier IV, meaning that the entire facility offers a cer- tain level of redundancy to support a cer- tain availability (say, 99.99% in a mission- critical case). Chances are, however, that some tasks in a given data center require less availability than others; in these cases, jobs for which 99% availability is sufficient constitute a tremendous waste of resources when they operate on 99.99%-availability infrastructure. us, subdivision of the de- sign into availability tiers can greatly reduce capex, since less infrastructure is dedicated to tasks that don't need it, and opex, thanks to declines in a range of ongoing costs such as maintenance, financing, energy and so on. is design approach is effectively an extension of the multi-zone data center, which offers "a method of reducing capital expense dramatically since the electrical/ mechanical equipment required was oen reduced, while still maintaining scalability in the data center," according to Gartner Research VP David J. Cappuccio. Multi- zone data centers support differing power- density levels in different areas, enabling reduction of infrastructure like power distribution and cooling for certain zones while providing more for the zones that truly need it. In addressing multiple avail- ability zones, Cappuccio said, "Rather than build a tier 4 fully redundant data center that supports all mission critical systems, and everything else, why not build a tier 4 zone that supports mission critical (which may only be 15% of my overall workload), and assign tier 1, 2, or 3 status to other ar- eas in the same building?" He suggests that a design combination of power zones and multiple tiers can cut capex by some 40%. WHY USE A MULTI-TIERED APPROACH? e official requirements of a Tier IV data center versus a Tier I data center are huge—to say nothing about the differ- ence relative to a data center that avoids the requirements of the Uptime Institute's tier classification system altogether. For instance, according to a summary in an HP white paper ("e Multi-tiered Hybrid Data Center"), a Tier IV facility targeting 99.995% availability (less than 30 minutes of downtime per year) must incorporate 2N generator and UPS systems, dual-active utility feeders, a 2N mechanical system and so on. For Tier I, which targets 99.671% availability (about 30 hours of downtime per year), the requirements are much more lax: the generator is optional, only a single UPS is called for and so on. e difference in capital costs alone between the highest and lowest tiers is stag- gering. If a data center is running, say, just 10% mission-critical tasks, 90% of the ser- vices would be overprovisioned with fault- tolerant infrastructure if the entire facility is designed exclusively for Tier IV operation. By creating a multi-tiered modular design, that 10% could be served with the required infrastructure while providing only what is needed (maybe a single backup generator instead of two—or, more broadly, N instead of 2N) for less critical functions, all while following a strategy of adding infrastruc- ture only when it is needed. Although the monolithic single-tier design approach ensures consistency across the data center—any function can, for instance, be deployed in any rack without losing mission-critical capability—HP esti- mates that "as many as 50 percent of the ap- plications running in the typical data center could be classified as less than business- critical. us, even a simple two-tier model could avoid some of the inefficiencies and cost premiums of a single-tier design. e list below summarizes the potential benefits of a multi-tiered design strategy: • Lower capital outlays. Higher-tier deployments require more redun- dant infrastructure, which means higher capital costs. ese costs are compounded when the facility is financed rather than purchased outright. Lower-tier applications are thus overprovisioned, reducing cost efficiency. • Lower operating costs. More infrastructure typically means more energy consumption, which increases opex. Tailoring the infra- structure to the application—that is, not provisioning mission-critical infrastructure for less critical func- tions—improves energy efficiency. • Less maintenance. Every piece of equipment in the data center is another item that requires main- tenance, from UPS systems to generators and more. Maintenance costs both time and money, moving the focus from the core business to infrastructure. • More space. By cutting some of the supporting infrastructure for less critical tasks, the multi-tiered ap- proach opens precious space in the data center for future growth. Given the tremendous construction costs for just the building, this approach can help extend the life of the facility and thus save money. • More flexibility and scalability. e modular approach of a multi-tiered data center enables more operating models and leaves more resources The difference in capital costs alone between the highest and lowest tiers is staggering. If a data center is running, say, just 10% mission-critical tasks, 90% of the services would be overprovisioned with fault-tolerant infrastructure if the entire facility is designed exclusively for Tier IV operation. By creating a multi-tiered modular design, that 10% could be served with the required infrastructure while providing only what is needed (maybe a single backup generator instead of two—or, more broadly, N instead of 2N) for less critical functions, all while following a strategy of adding infrastructure only when it is needed.