By continuing our exploration of the building blocks that make up a WebSphere eXtreme Scale deployment, we delve further into shards, partitions, and replication in this chapter. Our focus this time is data availability. In Chapter 5, we learned how to create a scale-out deployment emphasizing total capacity. We'll now look at building redundancy into our deployment with replication. We'll look at reasons to add replication to a deployment and at the two different replica types.
Before we proceed, you should have a firm understanding of the relationship between shards and partitions. We use the xsadmin
tool and container log files to get a better idea of how shard placement and startup works. As we use xsadmin
, we find out that shards can move around a deployment at runtime. This is known as shard migration.
Shard migration plays an important role in WebSphere eXtreme Scale's flexibility. As shards can migrate from container to container, we find that it is...