Storage class | replicas?


#1

Hello,

I am trying to understand the concept of Longhorn storage class replica setting. I am bit confused because about it because when I deploy HA Elasticsearch or HA Kafka I am using already 3 nodes.

ElasticSearch:
master -> replica 3 with 3 PVC’s (PV) on 3 different nodes
data -> replica 3 with 3 PVC’s (PV) on 3 different nodes
Total 6 PV on 3 different nodes (2 for each)

Kafka:
Zookeeper -> replica 3 with 3 PVC’s (PV) on 3 different nodes
Kafka -> replica 3 with 3 PVC’s (PV) on 3 different nodes
Total 6 PV on 3 different nodes (2 for each)

Mysql cluster …

SO, 12 PV on 3 nodes
Now comes the confusion…
12 PVC (PV) with storage class replica set to 3 -> 36 ??? Wow.
I think I don’t understand the concept :slight_smile:

I someone willing to explain?


#2

Hi @houtenvan

Longhorn itself is a generic block storage solution with replications. If the applications already have replications enabled, you may not need Longhorn’s replicas. You can set the NumberOfReplica to 1 in the Longhorn StorageClass definition in this case.