Erasure struct {
		Version string `json:"version"` // Version of 'xl' format.
		Disk    string `json:"drive"`   // Disk field carries assigned disk uuid.
		// JBOD field carries the input disk order generated the first
		// time when fresh disks were supplied.
		JBOD []string `json:"jbod"`
	} `json:"xl"` // Erasure field holds xl format.
}

// Represents the V2 backend disk structure version
// under `.minio.sys` and actual data namespace.

- Some Unformatted - format all and return success.
- Any JBOD inconsistent - return failure
- Some are corrupt (missing format.json) - return failure
- Any unrecognized disks - return failure

Some disks are offline and we have quorum.
-----------------
- Some unformatted - format all and return success,
  treat disks offline as corrupted.
- Any JBOD inconsistent - return failure
- Some are corrupt (missing format.json)