@Jack, we write to 2 and read from 1. I do not understand why RF=2 matters here, will it have impact on the repair? Can you please explain more?
I select RF=2 in each region, because: 1. all 2 writes will be sent to local region, so we do not need to wait for the response across region. 2. if one node has problem in local region, the read can still hit the other one in local region as well. However, I can change the RF if it's really the cause of the under-counting. Thanks Dikang. On Thu, Mar 24, 2016 at 7:17 AM, Jack Krupansky <jack.krupan...@gmail.com> wrote: > 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 >> >> > -- Dikang
