Risks of cluster-init to increase server quota in a 2.2 cluster

I have a 13 node cluster that I want to increase ramsize (http://www.couchbase.com/docs/couchbase-manual-2.0/couchbase-admin-tasks...) to use more ram per server.
The reason is I am rebalancing 4 nodes out( currently 17 in ) and those 4 had significantly less RAM than the rest.

I want to go from a 52G to 100G, this nodes have 141G of RAM.

First question is, how risky is it? will the memcached process just allocate the extra ram inmediately? or will restarts happen? Should I expect data issues or performance issues? How long does it take?

Second, is 100G a reasonable number on 141G servers?


1 Answer

« Back to question.

Hi there, you should be totally fine to go ahead and increase that quota. The change will happen immediately, and there's no impact to perform or behavior.

All the change is really doing is "allowing" the memcached process to allocate more RAM as needed.

Increasing is totally fine. Even decreasing is fine, but you have to be more careful if decreasing the quota will lead to data being ejected from RAM and therefore cause more reads to come from disk.

And yes, 100G is find for a server that has 141. I would say you could go as high as 112 being safe.

Hope that helps