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From A J <>
Subject Re: Meaning of 'nodetool repair has to run within GCGraceSeconds'
Date Tue, 12 Jul 2011 15:01:55 GMT
Just confirming. Thanks for the clarification.

On Tue, Jul 12, 2011 at 10:53 AM, Peter Schuller
<> wrote:
>> From "Cassandra the definitive guide" - Basic Maintenance - Repair
>> "Running nodetool repair causes Cassandra to execute a major compaction.....
>> During a major compaction (see “Compaction” in the Glossary), the
>> server initiates a
>> TreeRequest/TreeReponse conversation to exchange Merkle trees with neighboring
>> nodes."
>> So is this text from the book misleading ?
> It's just being a bit less specific (I suppose maybe misleading can be
> claimed). If you repair everything on a node, that will imply a
> validating compaction (i.e., do the read part of the compaction stage
> but don't merge to and write new sstables) which is expensive for the
> usual reasons with disk I/O; it's "major" since it covers all data.
> The data read is in fact used to calculate a merkle tree for
> comparison with neighbors, as claimed.
> --
> / Peter Schuller

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