Ceph supports two types of weight sets:
- #. A **compat** weight set is a single alternative set of weights for each
- device and each node in the cluster. Compat weight sets cannot be expected
- to correct all anomalies (for example, PGs for different pools might be of
- different sizes and have different load levels, but are mostly treated
- alike by the balancer). However, they have the major advantage of being
- *backward compatible* with previous versions of Ceph. This means that even
- though weight sets were first introduced in Luminous v12.2.z, older
- clients (for example, Firefly) can still connect to the cluster when a
- compat weight set is being used to balance data.
-
- #. A **per-pool** weight set is more flexible in that it allows placement to
- be optimized for each data pool. Additionally, weights can be adjusted
- for each position of placement, allowing the optimizer to correct for a
- subtle skew of data toward devices with small weights relative to their
- peers (an effect that is usually apparent only in very large clusters
- but that can cause balancing problems).
+#. A **compat** weight set is a single alternative set of weights for each
+ device and each node in the cluster. Compat weight sets cannot be expected
+ to correct all anomalies (for example, PGs for different pools might be of
+ different sizes and have different load levels, but are mostly treated alike
+ by the balancer). However, they have the major advantage of being *backward
+ compatible* with previous versions of Ceph. This means that even though
+ weight sets were first introduced in Luminous v12.2.z, older clients (for
+ example, Firefly) can still connect to the cluster when a compat weight set
+ is being used to balance data.
+
+#. A **per-pool** weight set is more flexible in that it allows placement to
+ be optimized for each data pool. Additionally, weights can be adjusted
+ for each position of placement, allowing the optimizer to correct for a
+ subtle skew of data toward devices with small weights relative to their
+ peers (an effect that is usually apparent only in very large clusters
+ but that can cause balancing problems).
When weight sets are in use, the weights associated with each node in the
hierarchy are visible in a separate column (labeled either as ``(compat)`` or