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APIC-Cluster fail - Scalabilityl imit

Heinz Kern
Level 1
Level 1

Hello, we have a APIC-cluster of 5 nodes. my question if 2 fail:

  1. will the remaining ones taleover the shards so that the cluster is read-write or will i be in read-only mode?
  2. what happens to the scalability limit? will there be issues with switches or is it just a soft limit (meaning that i also could have 200 switches with 3 apics but no official support)

hope it is clear

 

br + thx

1 Accepted Solution

Accepted Solutions

Correct.  Shard distribution doesn't change unless the cluster size changes.  If you have a failure of any controller, the expectation is that it should be coming back into operation.   There's also the concern about scale support.  The only reason to extend beyond 3 APICs is to accomodate scale increase.  If all shards were replicated to remaining controllers in a larger cluster, it could quickly exceed the supported/tested scale limits for the controller.  This also saves unnecessary DB shuffling activity.  If you change the cluster size, then the lost shards will be replicated from the remaining copy on the master, but the fabric scale would be decreased also.  

Replacing a failed controller with a standby would help you regain full R/W operations as you would be restored to a majority across all shard replicas.

Robert

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