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25If It's Important, You Better Get Two

Whether it's a server, a router, or a business analyst, if your business relies on it, you need to have more than one. There are many gotchas in redundancy. Let's review some of the more significant ones:

• Each individual node needs to operate below 50% capacity. If the workload on each device is over 50%, and one fails, the remaining node will be overtaxed, and it will fail as well. This is a tricky problem. As server load slowly moves from 40 to 50 to 60% utilized, it's still a happy server, and no alerts or warnings are produced. However, the moment node A fails, the 60% load on node B becomes 120%, and now you have an outage. If you convinced your CFO to invest in redundancy, and this happens, you've got some explaining to do. The moment your utilization crosses 50%, you no longer have redundancy. To avoid this scenario, set your alerts at 45%: 45% utilized is actually 90% utilized, and therefore it's time to add capacity.
• Two of everything costs twice as much, or more, than one of everything. If one 10 gig internet circuit costs $5,000/month, guess how much two 10 gig internet circuits cost? If you said $10,000, you got it right. And remember, we need to run these circuits at less than 50% utilization, so redundant internet circuits double your costs with no additional capacity. The story gets worse. To manage two circuits, you need two network switches, two VPN concentrators, two firewalls, and dual power. You need private IP space, ...