Correct number recommendations

The mathematics of the current recommendations didn't seem to give the right outcomes. Especially with `U`, as you need at least `U+1` to keep availability in the face of `U` failures.
This commit is contained in:
Ben Harris 2015-10-09 10:37:12 +11:00
parent 79b70df747
commit 92137e89dc

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@ -80,8 +80,9 @@ Second, decide how many clusters should be able to be unavailable at the same ti
the number that can be unavailable `U`. If you are not sure, then 1 is a fine choice. the number that can be unavailable `U`. If you are not sure, then 1 is a fine choice.
If it is allowable for load-balancing to direct traffic to any region in the event of a cluster failure, then If it is allowable for load-balancing to direct traffic to any region in the event of a cluster failure, then
you need `R + U` clusters. If it is not (e.g you want to ensure low latency for all users in the event of a you need at least the larger of `R` or `U + 1` clusters. If it is not (e.g you want to ensure low latency for all
cluster failure), then you need to have `R * U` clusters (`U` in each of `R` regions). In any case, try to put each cluster in a different zone. users in the event of a cluster failure), then you need to have `R * (U + 1)` clusters
(`U + 1` in each of `R` regions). In any case, try to put each cluster in a different zone.
Finally, if any of your clusters would need more than the maximum recommended number of nodes for a Kubernetes cluster, then Finally, if any of your clusters would need more than the maximum recommended number of nodes for a Kubernetes cluster, then
you may need even more clusters. Kubernetes v1.0 currently supports clusters up to 100 nodes in size, but we are targeting you may need even more clusters. Kubernetes v1.0 currently supports clusters up to 100 nodes in size, but we are targeting