What CL do you read and write with? Normally, RF=2 is not recommended since it doesn't give you HA within a data center - there is no way to achieve quorum in the data center if a node goes down.
I suppose you can achieve a quorum if your request is spread across all three data centers, but normally apps try to issue requests to a local data center for performance. Having to ping all data centers on all requests to achieve a quorum seems a bit excessive. Can you advise us on your thinking when you selected RF=2? -- Jack Krupansky On Thu, Mar 24, 2016 at 2:17 AM, Dikang Gu <dikan...@gmail.com> wrote: > Hello there, > > We are experimenting Counters in Cassandra 2.2.5. Our setup is that we > have 6 nodes, across three different regions, and in each region, the > replication factor is 2. Basically, each nodes holds a full copy of the > data. > > When are doing 30k/s counter increment/decrement per node, and at the > meanwhile, we are double writing to our mysql tier, so that we can measure > the accuracy of C* counter, compared to mysql. > > The experiment result was great at the beginning, the counter value in C* > and mysql are very close. The difference is less than 0.1%. > > But when we start to run the repair on one node, the counter value in C* > become much less than the value in mysql, the difference becomes larger > than 1%. > > My question is that is it a known problem that the counter value will > become under-counted if repair is running? Should we avoid running repair > for counter tables? > > Thanks. > > -- > Dikang > >
