Redundancy vs Resiliency
What’s your biggest concern
about technology?
1That you’re going to
spend a lot of money.
2That it’s going to be
broken more often than it’s working.
So what you’re seeking is a highly available solution.
The problem is, you can’t buy a box
of availability…
You have to build it.
Redundancy
Everyone gets redundancy.
It’s two of something.
ChassisModules
Links
2 Tacos
A backup for the primary if it fails.
Here’s an example.
We have redundant cables connecting the
buildings together.
If one cable fails, we can use the other!
But what happens if a back-hoe takes out the conduit that houses both
cables?
Our redundancy was defeated by a single
event.
This is where Resiliency comes in.
Resiliency builds on top of Redundancy.
Resiliency provides the ability to…Recover, Converge
Self-Heal
So let’s update our example with some resiliency.
Now we can lose a conduit or a cable, and our
redundancy survives.
So what are some additional things we can
do inside the building?
Ensure separate demarcation entry points for power,
telecommunications and data.
1
Create separate cable paths within the building.
2
Keep redundant hardware in separate rooms within
the building.
3
Keeping redundant hardware in separate rooms
is GOOD.
Distributing redundant hardware
across the two buildings is BETTER.
The goal is to ensure that no single event can
defeat our redundancy.
So with redundancy and resiliency, we have a bulletproof physical
design.
Cool… we’re done,right?
Not exactly.
This is a great foundation. But…
We still need to talk about the traffic flowing across the link…
Here, traffic is balanced and performance
is excellent.
But when link A fails, all of it’s traffic goes to link B.
Now we have too much traffic on link B and performance is poor.
By introducing logical resiliency, we could have
avoided this problem.
Quality of Service (QoS) would allow us to permit business critical traffic
ONLY…
These guys don’t count as business critical traffic.
Now, if a circuit fails, we have plenty of bandwidth for our
business applications.
At this point, we have a RESILIENT solution.
All too often, the focus is REDUNDANCY, with RESILIENCY
getting little to no love.
To achieve high availability, the design MUST be resilient.
Resiliency automatically includes redundancy.
And there are many, many
layers to a network.
Design Matters
Redundancy and resiliency are the key to success in
your network design.
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