In a spinning drive set up, we've seen the performance go down 8X after replication is enabled. This is too much a hit for us. I've read a published performance tip that recommends turning off replication then then it back on to avoid duplication indexing. But we would really love to be able to continuously replicate our data.
Our set up is two instances on spinning drives. The IO wait is maxed and appears to be the bottleneck. With duplicate indexing we'd expect to close to 2X penalty but any explaination why it's 8X?