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From Viktor Jevdokimov <>
Subject RE: nodetool repair -pr enough in this scenario?
Date Tue, 05 Jun 2012 06:44:59 GMT
Understand simple mechanics first, decide how to act later.

Without -PR there's no difference from which host to run repair, it runs for the whole 100%
range, from start to end, the whole cluster, all nodes, at once.

With -PR it runs only for a primary range of a node you are running a repair.
Let say you have simple ring of 3 nodes with RF=2 and ranges (per node) N1=C-A, N2=A-B, N3=B-C
(node tokens are N1=A, N2=B, N3=C). No rack, no DC aware.
So running repair with -PR on node N2 will only repair a range A-B, for which node N2 is a
primary and N3 is a backup. N2 and N3 will synchronize A-B range one with other. For other
ranges you need to run on other nodes.

Without -PR running on any node will repair all ranges, A-B, B-C, C-A. A node you run a repair
without -PR is just a repair coordinator, so no difference, which one will be next time.

Best regards / Pagarbiai
Viktor Jevdokimov
Senior Developer

Phone: +370 5 212 3063, Fax +370 5 261 0453
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From: David Daeschler []
Sent: Tuesday, June 05, 2012 08:59
Subject: nodetool repair -pr enough in this scenario?


Currently I have a 4 node cassandra cluster on CentOS64. I have been running nodetool repair
(no -pr option) on a weekly schedule like:

Host1: Tue, Host2: Wed, Host3: Thu, Host4: Fri

In this scenario, if I were to add the -pr option, would this still be sufficient to prevent
forgotten deletes and properly maintain consistency?

Thank you,
- David

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