On Tue, Jun 5, 2012 at 8:44 AM, Viktor Jevdokimov < viktor.jevdoki...@adform.com> wrote:
> 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. > That's not exactly true. A repair without -pr will repair all the ranges of the node on which repair is ran. So it will only repair the ranges that the node is a replica for. It will *not* repair the whole cluster (unless the replication factor is equal to the number of nodes in the cluster but that's a degenerate case). And hence it does matter on which host repair is run (it always matter, whether you use -pr or not). In general you want to use repair without -pr in case where you want to repair a specific node. Typically, if a node was dead for a reasonably long time, you may want to run a repair (without -pr) on that specific node to have him catch up faster (faster that if you were only relying on read-repair and hinted-handoff). For repairing a whole cluster, as is the case for the weekly scheduled repairs in the initial question, you want to use -rp. You *do not* want to use repair without -pr in that case. You do not because for that task using -pr is more efficient (and to be clear, not using -pr won't cause problems, but it does is less efficient). -- Sylvain > > > 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 > > Email: viktor.jevdoki...@adform.com > Phone: +370 5 212 3063, Fax +370 5 261 0453 > J. Jasinskio 16C, LT-01112 Vilnius, Lithuania > Follow us on Twitter: @adforminsider <http://twitter.com/#!/adforminsider> > What is Adform: watch this short video <http://vimeo.com/adform/display> > [image: Adform News] <http://www.adform.com> > > Disclaimer: The information contained in this message and attachments is > intended solely for the attention and use of the named addressee and may be > confidential. If you are not the intended recipient, you are reminded that > the information remains the property of the sender. You must not use, > disclose, distribute, copy, print or rely on this e-mail. If you have > received this message in error, please contact the sender immediately and > irrevocably delete this message and any copies. > > *From:* David Daeschler [mailto:david.daesch...@gmail.com] > *Sent:* Tuesday, June 05, 2012 08:59 > *To:* user@cassandra.apache.org > *Subject:* nodetool repair -pr enough in this scenario?**** > > ** ** > > Hello,**** > > ** ** > > 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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