Hi Chris, Using pr with incremental repairs does not make sense. Primary range repair is an optimization over full repair. If you run full repair on a n node cluster with RF=3, you would be repairing each data thrice. E.g. in a 5 node cluster with RF=3, a range may exist on node A,B and C . When full repair is run on node A, the entire data in that range gets synced with replicas on node B and C. Now, when you run full repair on nodes B and C, you are wasting resources on repairing data which is already repaired. Primary range repair ensures that when you run repair on a node, it ONLY repairs the data which is owned by the node. Thus, no node repairs data which is not owned by it and must be repaired by other node. Redundant work is eliminated. Even in pr, each time you run pr on all nodes, you repair 100% of data. Why to repair complete data in each cycle?? ..even data which has not even changed since the last repair cycle? This is where Incremental repair comes as an improvement. Once repaired, a data would be marked repaired so that the next repair cycle could just focus on repairing the delta. Now, lets go back to the example of 5 node cluster with RF =3.This time we run incremental repair on all nodes. When you repair entire data on node A, all 3 replicas are marked as repaired. Even if you run inc repair on all ranges on the second node, you would not re-repair the already repaired data. Thus, there is no advantage of repairing only the data owned by the node (primary range of the node). You can run inc repair on all the data present on a node and Cassandra would make sure that when you repair data on other nodes, you only repair unrepaired data. ThanksAnuj
Sent from Yahoo Mail on Android On Tue, Jun 6, 2017 at 4:27 PM, Chris Stokesmore<chris.elsm...@demandlogic.co> wrote: Hi all, Wondering if anyone had any thoughts on this? At the moment the long running repairs cause us to be running them on two nodes at once for a bit of time, which obivould increases the cluster load. On 2017-05-25 16:18 (+0100), Chris Stokesmore <c...@demandlogic.co> wrote: > Hi,> > > We are running a 7 node Cassandra 2.2.8 cluster, RF=3, and had been running > repairs with the -pr option, via a cron job that runs on each node once per > week.> > > We changed that as some advice on the Cassandra IRC channel said it would > cause more anticompaction and > http://docs.datastax.com/en/archived/cassandra/2.2/cassandra/tools/toolsRepair.html > says 'Performing partitioner range repairs by using the -pr option is > generally considered a good choice for doing manual repairs. However, this > option cannot be used with incremental repairs (default for Cassandra 2.2 and > later)' > > Only problem is our -pr repairs were taking about 8 hours, and now the non-pr > repair are taking 24+ - I guess this makes sense, repairing 1/7 of data > increased to 3/7, except I was hoping to see a speed up after the first loop > through the cluster as each repair will be marking much more data as > repaired, right?> > > > Is running -pr with incremental repairs really that bad? > --------------------------------------------------------------------- To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org For additional commands, e-mail: user-h...@cassandra.apache.org
