The best replacement for cluster is migraine.

The best alternatives to cluster are rated as following:
★★★★★  migraine
★★★  stratified sampling
★★★  sector
★★★  grid
★★  outbreak
★  tension headache
★  digraph
★  load balancing
★  sinus headache
★  stratified
★  cloud
★  load balancer
★  replication
★  load balance
★  node
★  non cluster
  farm
  supercomputer
  mirror
  stratified sample
  sun cluster
  globular cluster
  vcs
  nlb
  smp
  stratified random sampling
  web farm
  resource pool
  single-server
  strata

Your alternative for cluster is not listed? Suggest!
Speaking about cluster, one probably shouldn't forget about load balancing.

Other search terms related to cluster and their ratings are:
★★★★★ load balancing
★★ hyper v
You have in mind a companion for cluster and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of cluster in all years. Click on graph for more.
cluster
migraine
stratified sampling