On 4/29/22 02:17, DAVID MARTIN NIETO wrote:
I make a similar question time ago and get this answer:
Expanding a little bit on what I wrote before:
If you have three ZK servers, you can lose one and remain fully operational.
If you have four ZK servers, you can still only lose one -- if you lose
two, then the remaining servers do not have a majority. It is not safe
to write to a ZK database if the quorum does not have majority.
At five servers, you can lose two and remain fully operational. If you
have six servers, you can still only lose two, because if you lost
three, then the remaining servers would not be a majority.
This is why an odd number is strongly recommended. An odd number is not
required. A minimum of three servers IS required.
A minimal fault tolerant SolrCloud setup would consist of three servers
all running on separate physical hardware. Two of the servers would run
Solr and ZooKeeper, and the third server would just run ZK. The
hardware requirements for the third server would be far less than the
other two. You could have a very old laptop or a raspberry pi and it
would likely work just fine.
Running three VMs for ZK on the same physical host is not fault
tolerant. If they physical host were to die, your ZK would completely
disappear.
Thanks,
Shawn
