Is a 2 nodes Clickhouse setup possible? If yes would it be bad or unreasonable?
Most tutorials require a 3 node setup. For example the official documentation: https://clickhouse.com/docs/en/guides/sre/keeper/clickhouse-keeper
I found this example with a two node setup and not sure if it's a good idea. https://kb.altinity.com/altinity-kb-setup-and-maintenance/altinity-kb-zookeeper/clickhouse-keeper/
The alternative would be to use the second server for backups (with https://github.com/AlexAkulov/clickhouse-backup) but would prefer a replication setup.
Thanks for any hint!
I found this example with a two node setup and not sure if it's a good idea.
I made this example. Some people use this in production, and they are happy, though their ingestion rate is very low.
2 nodes is not a problem ( split brain is impossible with Keeper and Zookeeper ). But with 2 nodes of Keeper or Zookeeper you don't HighAvailability, if one node on Keeper is down, the second node stops to serve requests and Replicated tables in ClickHouse became readonly on all replicas.
Embedded Keeper or Keeper on the same server with ClickHouse is a bad idea if you have heavy loaded system with a high ingestion rate. ClickHouse server utilizes all CPU and all I/O, so Keeper or Zookeeper produce timeout errors because they starve for CPU and especially I/O (disk is too slow for them).