I recommend figuring out the latency between your datacenters. Cassandra isn’t going to be any more than that barring JVM pauses on the remote coordinator.
> On Oct 17, 2017, at 4:17 PM, Bill Walters <billwalter...@gmail.com> wrote: > > Hi Everyone, > > I need some suggestions on finding the time taken for Cassandra replication > to happen from east to west region for write and read operations on a multi > DC cluster. > Currently, below is our cluster setup. > > Cassandra version: DSE 5.0.7 > No of Data centers: 2 (AWS East and AWS West regions) > No of Nodes: 12 nodes (6 nodes in AWS East and 6 nodes in AWS West) > Replication Factor: 3 in each data center. > Cluster size: Around 40 GB on each node > > Sometime, next year we have an activity where our clients are going to be > reading only from AWS West region. The data center in AWS east will be > available but we do not want any reads to be done on this.(Our management > wants to know the time it takes for Cassandra to replicate from one DC to the > other) > > Here are some options I have thought of in finding the time taken for > Cassandra replication to happen from AWS East DC to AWS West DC. > > 1. Setup a Java client to write/read a transaction with "Local Quorum" > consistency level in AWS East region as Local data center, capture the time > taken for this activity. Similarly use this client to perform read/write > transaction with "Local Quorum" consistency level in AWS West region and > capture the time. Then finally perform the same transaction with with "Each > Quorum" consistency level and capture the time. > > Inter DC latency = Time taken for Each Quorum transaction - (Time taken for > Local Quorum transaction in AWS East as local dc) - (Time taken for Local > Quorum transaction in AWS West as local dc). > > > 2. Utilize the > https://github.com/gitaroktato/cassandra-replication-latency-tools > <https://github.com/gitaroktato/cassandra-replication-latency-tools> open > source project where a Python Cassandra clients writes in one Data Center and > other client reads in other data center. > > > Can you please suggest if my strategies above will help in finding the Inter > DC latency or there are other ways I need to follow. > > > Thank You, > Bill Walters.
