Add large bucket support for erasure coded backend (#5160)

This PR implements an object layer which
combines input erasure sets of XL layers
into a unified namespace.

This object layer extends the existing
erasure coded implementation, it is assumed
in this design that providing > 16 disks is
a static configuration as well i.e if you started
the setup with 32 disks with 4 sets 8 disks per
pack then you would need to provide 4 sets always.

Some design details and restrictions:

- Objects are distributed using consistent ordering
  to a unique erasure coded layer.
- Each pack has its own dsync so locks are synchronized
  properly at pack (erasure layer).
- Each pack still has a maximum of 16 disks
  requirement, you can start with multiple
  such sets statically.
- Static sets set of disks and cannot be
  changed, there is no elastic expansion allowed.
- Static sets set of disks and cannot be
  changed, there is no elastic removal allowed.
- ListObjects() across sets can be noticeably
  slower since List happens on all servers,
  and is merged at this sets layer.

Fixes #5465
Fixes #5464
Fixes #5461
Fixes #5460
Fixes #5459
Fixes #5458
Fixes #5460
Fixes #5488
Fixes #5489
Fixes #5497
Fixes #5496

cmd/xl-v1-object_test.go

@@ -136,7 +136,7 @@ func TestXLDeleteObjectDiskNotFound(t *testing.T) {
 	// for a 16 disk setup, quorum is 9. To simulate disks not found yet
 	// quorum is available, we remove disks leaving quorum disks behind.
 	for i := range xl.storageDisks[:7] {
-		xl.storageDisks[i] = newNaughtyDisk(xl.storageDisks[i].(*retryStorage), nil, errFaultyDisk)
+		xl.storageDisks[i] = newNaughtyDisk(xl.storageDisks[i], nil, errFaultyDisk)
 	}
 	err = obj.DeleteObject(bucket, object)
 	if err != nil {
@@ -196,10 +196,10 @@ func TestGetObjectNoQuorum(t *testing.T) {
 		}
 		for i := range xl.storageDisks[:9] {
 			switch diskType := xl.storageDisks[i].(type) {
-			case *retryStorage:
-				xl.storageDisks[i] = newNaughtyDisk(diskType, diskErrors, errFaultyDisk)
 			case *naughtyDisk:
 				xl.storageDisks[i] = newNaughtyDisk(diskType.disk, diskErrors, errFaultyDisk)
+			default:
+				xl.storageDisks[i] = newNaughtyDisk(xl.storageDisks[i], diskErrors, errFaultyDisk)
 			}
 		}
 		// Fetch object from store.
@@ -247,10 +247,10 @@ func TestPutObjectNoQuorum(t *testing.T) {
 		}
 		for i := range xl.storageDisks[:9] {
 			switch diskType := xl.storageDisks[i].(type) {
-			case *retryStorage:
-				xl.storageDisks[i] = newNaughtyDisk(diskType, diskErrors, errFaultyDisk)
 			case *naughtyDisk:
 				xl.storageDisks[i] = newNaughtyDisk(diskType.disk, diskErrors, errFaultyDisk)
+			default:
+				xl.storageDisks[i] = newNaughtyDisk(xl.storageDisks[i], diskErrors, errFaultyDisk)
 			}
 		}
 		// Upload new content to same object "object"