1.3.2. Red Hat Ceph Storage backfill and recovery operations
When a Ceph OSD is removed, Red Hat Ceph Storage uses backfill and recovery operations to rebalance the cluster. Red Hat Ceph Storage does this to keep multiple copies of data according to the placement group policy. These operations use system resources. If a Red Hat Ceph Storage cluster is under load, its performance drops as it diverts resources to backfill and recovery.
To mitigate this performance effect during OSD removal, you can reduce the priority of backfill and recovery operations. The trade off for this is that there are less data replicas for a longer time, which puts the data at a slightly greater risk.
The parameters detailed in the following table are used to configure the priority of backfill and recovery operations.
| Parameter | Description | Default value |
|---|---|---|
|
| Sets the priority for recovery operations, relative to the OSD client OP priority. | 3 |
|
| Sets the number of active recovery requests per OSD, at one time. More requests accelerate recovery, but the requests place an increased load on the cluster. Set this to 1 if you want to reduce latency. | 3 |
|
| Sets the maximum number of backfills allowed to or from a single OSD. | 1 |
