mClock clients

The mClock scheduler handles requests from different types of Ceph services. Each service is considered by mClock as a type of client. Depending on the type of requests handled, mClock clients are classified into different bucket types.

The different bucket classification types are as follows:

• Client - Handles input and output (I/O) requests issued by external clients of Ceph.

• Background recovery - Handles internal recovery requests.

• Background best-effort - Handles internal backfill, scrub, snap trim, and placement group (PG) deletion requests.

The mClock scheduler derives the cost of an operation used in the QoS calculations from osd_mclock_max_capacity_iops_hdd | osd_mclock_max_capacity_iops_ssd, osd_mclock_max_sequential_bandwidth_hdd | osd_mclock_max_sequential_bandwidth_ssd, and osd_op_num_shards_hdd | osd_op_num_shards_ssd parameters.