Tuning tiering

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.

Flushing and eviction

The main tuning options that should be looked at first are the ones that define the size limit to the top tier, when it should flush and when it should evict...