pick disks which are common maximally used (#10600)

further optimization to ensure that good disks
are always used for listing, other than healing
we only use disks that are maximally used.

pkg/disk/disk.go

@@ -25,10 +25,8 @@ package disk
 type Info struct {
 	Total  uint64
 	Free   uint64
+	Used   uint64
 	Files  uint64
 	Ffree  uint64
 	FSType string
-
-	// Usage is calculated per tenant.
-	Usage uint64
 }