Apache Cassandra : Does running nodetool repair with the full option on one node sufficient, or must it be run on every single node?

Question

We currently run nodetool repair with the -pr option on every single node every weekend , and as the literature suggests run the repairs with the full option once every month on all nodes .

Is it enough to run the repair with the full option for one node per datacenter ?

Currently running on AWS Ec2 instances in a single region with 2 datacenters.

Answer 1

it is always best to run nodetool repair --partitioner-range (or -pr in shorthand) one node at a time across the entire cluster.

here is another article that explains about repairs.

Answer 2

The short answer is No, you can't run the full repair on a single node even if you've been running nodetool repair -pr regularly on all the nodes.

Here's an example. Suppose you have 5 nodes and RF = 3. The 3 replicas will be divided across 5 nodes. Another way of saying this is that each node will have 3/5 of the data. Running nodetool repair -full on a single node will not be able to repair all of the data. Therefore, you have to run the full repair on all of the nodes.