Load Balanced Servers
A single server presents a single point of failure. It's important to remember that increasing availability is a exponentially expensive proposition, as the following table demonstrates.
Uptime Desired (Increasing Cost -->) |
||||
| 99% (2 Nines) |
99.9% (3 Nines) | 99.99% (4 Nines) | 99.999% (5 Nines) | |
| Hours Down/Year | 87.6 (!) | 8.76 | ~1 (53 minutes) | ~ 0 (5 minutes) |
| Appropriate Solution (in terms of uptime) | Shared Service | Shared Service/Dedicated Server | N+1 Server Cluster (2 Servers) | 2N + 1 Servers for each service |
| Estimated Annual Cost | < £100 | £100 - £6,000 | ~ £12,000 | £18,000 - £XXX,XXX |
| Appropriate Solution (in terms of uptime) | Shared Service | Shared Service/Dedicated Server | Load balanced cluster | Load balanced cluster |
Achieving each new "9" dramatically reduces the tolerance for downtime while increasing the expense. The key with deciding on a solution is to be realistic and balance cost with requirement. Most organisations looking at high end server solutions such as clustering should be able to calculate how much an hour of downtime costs them. It's then easy enough to place yourself on the scale, for example, if an online retailer would lose ~£5,000 (in tangible sales) for being offline for an hour then it can easily justify the move from a "3 Nines" solution to a "4 Nines" solution based on a saving of ~£40,000 in lost trade (if the service was down for 0.1% of the time). This represents a good investment as it would have only cost an extra £6,000
It's important to remember that paying for "downtime insurance" is one of life's nasty catch 22's; if you don't do it you could get hurt, but it's possible that it'll never come to be needed, or more accurately because it was in place you noticed no downtime. As with all forms of preventive behaviour it's only after something goes wrong that you wished you'd invested more. Everyone has perfect hindsight.
Having said that server clusters are not required for all clients, so to find out if you might benefit from a no-obligation quote please contact us on the form below and we'd be happy to talk over your requirements.
Our Services: Dedicated Servers | Load Balanced Servers | Multihomed Transit