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Consider my current Cassandra cluster is following, DC1: 2 DC2: 2 each data center has 2 nodes and RF=2. Now i am adding 2 more data centers DC1: 2, DC2:2 , DC3: 2, DC4 : 2. So is it required to run nodetool repair on new nodes in DC3 and DC4. So far i read executing nodetool rebuild in the new DC is enough.

Also, i have one more query on when to run 'nodetool repair'. Please advise me.

Dinesh Kumar
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1 Answers1

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As you are adding the new DCs once you have changed the NetworkTopology replication factor to include the new DC a rebuild should be fine just make sure to specify the source DC as on of the preexisting DCs.

Here are detailed steps for adding a new DC.

In general you should be running a repair every week if you have the default GC Grace settings.

Jeff Beck
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  • Thanks. So when adding DC3, rebuild DC1 and rebuild DC2 must be run on all the nodes in DC3. Am i right? – Dinesh Kumar Oct 18 '16 at 03:32
  • Also one more question, Can we run repair on the nodes which has heavy read/write operations? – Dinesh Kumar Oct 18 '16 at 03:33
  • When you add DC 3 rebuild each node there targeted at DC 1 or 2 that's enough. – Jeff Beck Oct 18 '16 at 03:35
  • As for repairs they will need to be done regularly everywhere it will take tuning and addressed if you find issues as its own question. – Jeff Beck Oct 18 '16 at 03:36
  • Okay Thanks !!. So we can run repairs even if the node is loaded with read/write operations and we dont need to allocate any maintenance period to run repairs where the load will be less. – Dinesh Kumar Oct 18 '16 at 03:49
  • A repair will take days. – Jeff Beck Oct 18 '16 at 03:50
  • Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/125965/discussion-between-dinesh-kumar-and-jeff-beck). – Dinesh Kumar Oct 18 '16 at 03:54
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    @DineshKumar This might serve as some useful background reading on repair: http://www.datastax.com/dev/blog/repair-in-cassandra – markc Oct 19 '16 at 13:09