Each node is responsible of healing its local drives; Each drive will have multiple heal workers which is the quarter of the number of CPU cores of the node or the quarter of the configured nr_requests of the drive (https://www.kernel.org/doc/Documentation/block/queue-sysfs.txt). It is also possible to provide a custom number of workers by using this command: `mc admin config set alias/ heal drive_workers=100` .


```
~ mc admin config set alias/ heal

## Community Contribution License
All community contributions in this pull request are licensed to the project maintainers
under the terms of the [Apache 2 license](https://www.apache.org/licenses/LICENSE-2.0). 
By creating this pull request I represent that I have the right to license the 
contributions to the project maintainers under the Apache 2 license.

## Description


## Motivation and Context


## How to test this PR?

### Step 1: Ensure postgresql minimum requirements are met

MinIO requires PostgreSQL version 9.5 or above. MinIO uses the [`INSERT ON CONFLICT`](https://www.postgresql.org/docs/9.5/static/sql-insert.html#SQL-ON-CONFLICT) (aka UPSERT) feature, introduced in version 9.5 and the [JSONB](https://www.postgresql.org/docs/9.4/static/datatype-json.html) data-type introduced in version 9.4.

### Step 2: Add PostgreSQL endpoint to MinIO

The Eclipse Public License is available at
  https://www.eclipse.org/legal/epl-2.0/
and the Eclipse Distribution License is available at
  http://www.eclipse.org/org/documents/edl-v10.php.

For an explanation of what dual-licensing means to you, see:
https://www.eclipse.org/legal/eplfaq.php#DUALLIC

****

- BucketCORS (CORS enabled by default on all buckets for all HTTP verbs, you can optionally restrict the CORS domains)
- BucketWebsite (Use [`caddy`](https://github.com/caddyserver/caddy) or [`nginx`](https://www.nginx.com/resources/wiki/))
- BucketAnalytics, BucketMetrics, BucketLogging (Use [bucket notification](https://min.io/docs/minio/linux/administration/monitoring/bucket-notifications.html) APIs)

- Servers running distributed MinIO instances should be less than 15 minutes apart. You can enable [NTP](http://www.ntp.org/) service as a best practice to ensure same times across servers.
- `MINIO_DOMAIN` environment variable should be defined and exported for bucket DNS style support.