Removing nodes or scaling down the Vertica cluster is a fairly simple process. The procedure of removing nodes comprises the following broad steps:
Back up the database.
Remember that it is mandatory to lower the K-safety if the cluster is not able to sustain the current level of K-safety after the cluster is scaled down.
Remove the host from the database.
A database with a K-safety level 1 requires at least three nodes to operate, and a database with a K-safety level 2 requires at least five nodes to operate. Vertica doesn't support K-safety of level 3 and above. To lower the K-safety level, we will use the MARK_DESIGN_KSAFE function in the Vsql console, as shown in the following example:
km=> SELECT MARK_DESIGN_KSAFE(1); MARK_DESIGN_KSAFE ---------------------- Marked design 1-safe (1 row)