### OpenStack

- The `openstack-heat` provider for `kube-up` is deprecated and will be removed
  in a future release. Refer to Issue [#49213](https://github.com/kubernetes/kubernetes/issues/49213)
  for background information.

### Scheduling

    * Remove deprecated and unmaintained windows installer.  ([#58020](https://github.com/kubernetes/kubernetes/pull/58020), [@mikedanese](https://github.com/mikedanese))

    * Remove deprecated and unmaintained openstack-heat kube-up.sh.  ([#58021](https://github.com/kubernetes/kubernetes/pull/58021), [@mikedanese](https://github.com/mikedanese))

### Documentation

- Feat: azure file migration go beta in 1.21. Feature gates CSIMigration to Beta (on by default) and CSIMigrationAzureFile to Beta (off by default since it requires installation of the AzureFile CSI Driver)

    - `apiserver_flowcontrol_demand_seats_smoothed`: Smoothed seat demands
    - `apiserver_flowcontrol_target_seats`: Seat allocation targets
    - `apiserver_flowcontrol_seat_fair_frac`: Fair fraction of server's concurrency to allocate to each priority level that can use it

- Introduced new apiserver metric `apiserver_flowcontrol_current_inqueue_seats`. This metric is analogous to `apiserver_flowcontrol_current_inqueue_requests`, but tracks the total number of seats, as each request can take more than one seat. ([#119385](https://github.com/kubernetes/kubernetes/pull/119385), [@andrewsykim](https://github.com/andrewsykim))

* In 'kubectl describe', find controllers with ControllerRef, instead of showing the original creator. ([#42849](https://github.com/kubernetes/kubernetes/pull/42849), [@janetkuo](https://github.com/janetkuo))
* Heat cluster operations now support environments that have multiple Swift URLs ([#41561](https://github.com/kubernetes/kubernetes/pull/41561), [@jamiehannaford](https://github.com/jamiehannaford))

### OpenStack
* Do not daemonize `salt-minion` for the openstack-heat provider. ([#40722](https://github.com/kubernetes/kubernetes/pull/40722), [@micmro](https://github.com/micmro))

- Some apiserver metrics were changed, as follows.
  - `priority_level_seat_count_samples` is replaced with `priority_level_seat_utilization`, which samples every nanosecond rather than every millisecond; the old metric conveyed utilization despite its name.
  - `priority_level_seat_count_watermarks` is removed.

- Feat: add azure shared disk support ([#89511](https://github.com/kubernetes/kubernetes/pull/89511), [@andyzhangx](https://github.com/andyzhangx)) [SIG Cloud Provider and Storage]
- Feat: change azure disk api-version ([#89250](https://github.com/kubernetes/kubernetes/pull/89250), [@andyzhangx](https://github.com/andyzhangx)) [SIG Cloud Provider and Storage]

- This PR adds the following metrics for API Priority and Fairness.
  - **apiserver_flowcontrol_priority_level_seat_count_samples**: histograms of seats occupied by executing requests (both regular and final-delay phases included), broken down by priority_level; the observations are taken once per millisecond.