From 380326b5d1ba26a9c5943a8c09072ab45e1b9d1e Mon Sep 17 00:00:00 2001 From: Brandon Philips Date: Sat, 7 Sep 2013 09:05:24 -0700 Subject: [PATCH] feat(README): add note about cluster size Cluster size keeps coming up on IRC and the mailing list. Add an FAQ section. --- README.md | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/README.md b/README.md index a4ad5f1d4..a9df80200 100644 --- a/README.md +++ b/README.md @@ -495,6 +495,19 @@ If you are using SSL for server to server communication, you must use it on all - [mattn/etcd-vim](https://github.com/mattn/etcd-vim) - SET and GET keys from inside vim - [mattn/etcdenv](https://github.com/mattn/etcdenv) - "env" shebang with etcd integration +## FAQ + +### What size cluster should I use? + +Every command the client sends to the master is broadcast it to all of the followers. +But, the command is not be committed until the majority of the cluster machines receive that command. + +Because of this majority voting property the ideal cluster should be kept small to keep speed up and be made up of an odd number of machines. + +Odd numbers are good because if you have 8 machines the majority will be 5 and if you have 9 machines the majority with be 5. +The result is that an 8 machine cluster can tolerate 3 machine failures and a 9 machine cluster can tolerate 4 nodes failures. +And in the best case when all 9 machines are responding the cluster will perform at the speed of the fastest 5 nodes. + ## Project Details ### Versioning