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From Sachin Bhansali <>
Subject Re: Cassandra Replicas Down during Nodetool repair
Date Fri, 20 Jul 2012 17:18:40 GMT
I am developing an automated script for our server maintenance. It would
execute a nodetool repair ever weekend. We have 3 nodes in DC1 and 3 in
DC2. We are currently on Cassandra 0.8.4.

I am trying to understand effects of what would happens if connectivity
between DC1 and DC2 is lost or couple of replica goes down BEFORE or DURING
a nodetool repair. It could be a network issue, an network upgrade(which
usually happens on weekends),or something else. I understand that nodetool
repair computes a Merkle tree for each range of data on that node, and
compares it with the versions on other replicas. So if their is no
connectivity between replicas how would a nodetool repair behave ? Will it
really repair the nodes. Do i have to rerun node tool repair after all
nodes are up and connectivity is restored. Will their be any side effects
of this event which i need to handle ?

I goggled about it but couldn't find much details. Any insight would be

- Sachin

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