Unlike the majority of Ceph's features, which by default perform well for a large number of workloads, Ceph's tiering functionality requires careful configuration of its various parameters to ensure good performance. You should also have a basic understanding of your workload's I/O profile; tiering will only work well if your data has a small percentage of hot data. Workloads that are uniformly random or involve lots of sequential access patterns will either show no improvement or in some cases may actually be slower.