cluster on two nodes


Is it possible to run ES on two nodes (still having HA mode)?

Documentation states that in order to maintain quorum, cluster must contain at least 3 nodes. Is it possible to configure such things?

Not really, it works on a quorum. You could have three, with two real nodes and configure one as a witness though

Jame, thanks for info.

Can you clarify a little bit on “witness” mode. Is it some kind of special setting in node config? If so, could you please point me to some sample or documentation on this?

Also, one more thing - let’s assume that I setup 4 nodes (two machines, two nodes in each machine). If one machine dies (2 nodes left). Would quorum be still maintained in this scenario (sorry for my limited understanding of this algorithm)?

So a witness has data up to X age old, and you can recover during that time.

A quorum needs a majority so no running on two machines won’t work, you need an odd number.



Understood. Thanks for clarifications.

Will be able to configure… There are some changes that need to be added for witness functionality (not much but some). There are other models you can use for two nodes that have been discussed on this list as well. In general if you want consistency three is your best bet. The reason for this is that any form dealing with two has a possibility of running into a split brain scenario