Incorrect error message for insufficient volume fix (#6099)

Reply back with appropriate error message when the server is spawn
with volume of insufficient size (< 1GiB).

Fixes #5993.

cmd/fs-v1.go

@@ -112,6 +112,9 @@ func NewFSObjectLayer(fsPath string) (ObjectLayer, error) {
 
 	var err error
 	if fsPath, err = getValidPath(fsPath); err != nil {
+		if err == errMinDiskSize {
+			return nil, err
+		}
 		return nil, uiErrUnableToWriteInBackend(err)
 	}
 

cmd/posix.go

@@ -224,7 +224,7 @@ func checkDiskMinTotal(di disk.Info) (err error) {
 	// used for journalling, inodes etc.
 	totalDiskSpace := float64(di.Total) * 0.95
 	if int64(totalDiskSpace) <= diskMinTotalSpace {
-		return errDiskFull
+		return errMinDiskSize
 	}
 	return nil
 }

cmd/posix_test.go

@@ -1948,7 +1948,7 @@ func TestCheckDiskTotalMin(t *testing.T) {
 				FSType: "XFS",
 				Files:  9999,
 			},
-			err: errDiskFull,
+			err: errMinDiskSize,
 		},
 	}
 

cmd/storage-errors.go

@@ -76,6 +76,9 @@ var errBitrotHashAlgoInvalid = errors.New("bit-rot hash algorithm is invalid")
 // errCrossDeviceLink - rename across devices not allowed.
 var errCrossDeviceLink = errors.New("Rename across devices not allowed, please fix your backend configuration")
 
+// errMinDiskSize - cannot create volume or files when disk size is less than threshold.
+var errMinDiskSize = errors.New("The disk size is less than the minimum threshold")
+
 // hashMisMatchError - represents a bit-rot hash verification failure
 // error.
 type hashMismatchError struct {