Availability

For business-critical applications, availability is of paramount importance. The risk of downtime can stop revenue stream, cause assets to be under utilized and unproductive, increase wage costs, damage brand perception and induce legal costs.

How Availability is Calculated?

You can calculate availability using two averages (Mean Time Between Failure- MTBF) and recovery time from failure (Mean Time To Repair- MTTR).

Availability = MTBF / (MTTR+MTBF)

Highest availability is reached when MTBF is maximised and MTTR is minimised. All manufacturers have achieved extremely high MTBF values for their equipment.

Reducing Repair Time

A significant gain in availability comes from a significant reduction in the MTTR. Systems specifically designed to minimize MTTR now offer the highest availability. PowerWAVE®UPS systems offer the lowest MTTR in the industry and consequently the highest system availability.

The PowerWAVE®9000DPA, and PowerWAVE®9000 series bothfeature 'hot swap' UPS modules. In the unlikely event of a module failure, the UPS system can be repaired by simply replacing the faulty module, with no need to work on the system online or even to power it down. This allows a typical repair time of under 30 minutes compared with the 6 hours normally needed to shut down a legacy UPS and perform online repairs.

Achieving the best possible Availability - '6 nines'

This significant reduction in repair time means that PowerWAVE® technology brings an availability of 'Six Nines' (99.9999%) compared with the 'Five Nines' availability of earlier products.

This can be shown by comparing a legacy and a modular UPS system, both with an MTBF figure of 500,000 hours, and calculating the Availability for each:

Traditional system availability   500,000 Hrs MTBF 6 Hrs MTTR Availability = 500,000/(500,000+6) = 0.999988 or 99.9988% which can be rounded to 99.999% (Five Nines)

Modular system availability   500,000 Hrs MTBF 0.5 Hrs MTTR Availability = 500,000/(500,000+0.5) = 0.999999 or 99.9999% (Six Nines)

If 6 nines availability is not enough for your business applications you will need to consider additional redundancy and resiliency - read more