CODEWITHSUNDEEP
cluster-computinghigh-availability
Jimm
Jimm

Reputation: 8505

HA Minimal Cluster for 5- Nines

I am trying to find out if 3 node HA cluster is common practice? Most of the references on Google point to 2 node cluster. But i not able to convince myself that an application that require 5 Nine's, can implement 2 node HA cluster on commodity hardware. The reason behind it is simple. If a machine on which one node goes offline, then there will be only one node left without any back up. To reduce dependency on node that went offline, i think a 3 node cluster is a min requirement.

Upvotes: 0

Views: 236

Answers (1)

sdg
sdg

Reputation: 4723

In order to give a factual answer, much more data would be required.

But from an anecdotal perspective, two nodes of commodity hardware are not nearly enough to give you five-nines with any level of reliability (or at least sleep-at-night comfort).

Most cluster diagrams are likely drawn with only two nodes for ease of explanation, "If A fails, B keeps working".

Given your five-nines however, and "commodity hardware", I would consider more than three as a requirement; perhaps as many as five or more.

Remember to allow for network, power and perhaps even geographical diversity if you are really after that kind of reliability.

Upvotes: 1

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