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From Peter Schuller <>
Subject Re: Node repair questions
Date Mon, 11 Jul 2011 23:01:44 GMT
(not answering (1) right now, because it's more involved)

> 2. Does a Nodetool Repair block any reads and writes on the node,
> while the repair is going on ? During repair, if I try to do an
> insert, will the insert wait for repair to complete first ?

It doesn't imply any blocking. It's roughly similar to compaction in
its impact on nodes; in addition when data is streamed (if any) the
impact should be similar to node bootstrapping.

> 3. I read that repair can impact your workload as it causes additional
> disk and cpu activity. But any details of the impact mechanism and any
> ballpark on how much the read/write performance deteriorates ?

The compaction part will have an impact similar to regular compaction
except it's read-only (no writing of new sstables). It is subject to
compaction throttling if you run a version of Cassandra with
compaction throttling.

Streaming causes disk/networking load and is not yet rate limited like

In addition be aware that repair can cause disk space usage to
temporarily increase if there are significant differences to be

/ Peter Schuller

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