diff --git a/api.go b/api.go
index 4d52ab1d9..3005bafbe 100644
--- a/api.go
+++ b/api.go
@@ -25,8 +25,6 @@ import (
 	"io/ioutil"
 	"math"
 	"net/url"
-	"os"
-	"path"
 	"sort"
 	"strconv"
 	"strings"
@@ -811,45 +809,19 @@ func (api *API) Usage(ctx context.Context, remote bool) (map[string]NodeUsage, e
 	defer span.Finish()
 
 	nodeUsages := make(map[string]NodeUsage)
+
+	indexSizes, err := api.holder.Txf().IndexSizes()
+	if err != nil {
+		return nil, errors.Wrap(err, "getting index usage")
+	}
 	var totalSize int64
-
-	// Open storage directory.
-	dirName, err := expandDirName(api.server.dataDir)
-	if err != nil {
-		return nodeUsages, errors.Wrap(err, "expanding data directory")
-	}
-	dir, err := os.Open(dirName)
-	if err != nil {
-		return nodeUsages, errors.Wrap(err, "opening data directory")
-	}
-	defer dir.Close()
-
-	files, err := dir.Readdir(-1)
-	if err != nil {
-		return nodeUsages, errors.Wrap(err, "reading data directory")
+	for _, s := range indexSizes {
+		totalSize += s
 	}
 
-	// Read size on disk for each index directory.
-	indexSizes := make(map[string]int64)
-	for _, file := range files {
-		if !file.IsDir() {
-			continue
-		}
-		if api.holder.Txf().IsTxDatabasePath(file.Name()) {
-			continue
-		}
-		fullName := path.Join(dirName, file.Name())
-		indexSizes[file.Name()], err = directoryUsage(fullName)
-		if err != nil {
-			return nodeUsages, errors.Wrap(err, "getting disk usage")
-		}
-		totalSize += indexSizes[file.Name()]
-	}
-
-	capacity, err := api.server.systemInfo.DiskCapacity(api.server.dataDir)
-
+	capacity, err := api.server.systemInfo.DiskCapacity(api.holder.path)
 	if err != nil {
-		api.server.logger.Printf("failed to get disk capacity: %s", err)
+		api.server.logger.Printf("couldn't read disk capacity: %s", err)
 	}
 
 	// Insert into result.
@@ -879,35 +851,6 @@ func (api *API) Usage(ctx context.Context, remote bool) (map[string]NodeUsage, e
 	return nodeUsages, nil
 }
 
-func directoryUsage(fname string) (int64, error) {
-	var size int64
-
-	dir, err := os.Open(fname)
-	if err != nil {
-		return 0, errors.Wrap(err, "opening data subdirectory")
-	}
-	defer dir.Close()
-
-	files, err := dir.Readdir(-1)
-	if err != nil {
-		return 0, errors.Wrap(err, "reading data subdirectory")
-	}
-
-	for _, file := range files {
-		if file.IsDir() {
-			sz, err := directoryUsage(path.Join(fname, file.Name()))
-			if err != nil {
-				return 0, err
-			}
-			size += sz
-		} else {
-			size += file.Size()
-		}
-	}
-
-	return size, nil
-}
-
 // RecalculateCaches forces all TopN caches to be updated.
 // This is done internally within a TopN query, but a user may want to do it ahead of time?
 func (api *API) RecalculateCaches(ctx context.Context) error {
diff --git a/txfactory.go b/txfactory.go
index a72f451c3..521a9f0b3 100644
--- a/txfactory.go
+++ b/txfactory.go
@@ -18,6 +18,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"path"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -564,6 +565,81 @@ func (f *TxFactory) DumpAll() {
 	f.dbPerShard.DumpAll()
 }
 
+func (f *TxFactory) IndexSizes() (map[string]int64, error) {
+	switch f.types[0] {
+	case roaringTxn:
+		return f.diskUsageFromFilesystem()
+	default:
+		return nil, errors.New("Not implemented")
+	}
+
+}
+
+func (f *TxFactory) diskUsageFromFilesystem() (map[string]int64, error) {
+	// Open storage directory.
+	indexSizes := make(map[string]int64)
+	dirName, err := expandDirName(f.holder.path)
+	if err != nil {
+		return indexSizes, errors.Wrap(err, "expanding data directory")
+	}
+	dir, err := os.Open(dirName)
+	if err != nil {
+		return indexSizes, errors.Wrap(err, "opening data directory")
+	}
+	defer dir.Close()
+
+	files, err := dir.Readdir(-1)
+	if err != nil {
+		return indexSizes, errors.Wrap(err, "reading data directory")
+	}
+
+	// Read size on disk for each index directory.
+	for _, file := range files {
+		if !file.IsDir() {
+			continue
+		}
+		if f.IsTxDatabasePath(file.Name()) {
+			continue
+		}
+		fullName := path.Join(dirName, file.Name())
+		indexSizes[file.Name()], err = directoryUsage(fullName)
+		if err != nil {
+			return indexSizes, errors.Wrap(err, "getting disk usage")
+		}
+	}
+
+	return indexSizes, nil
+}
+
+func directoryUsage(fname string) (int64, error) {
+	var size int64
+
+	dir, err := os.Open(fname)
+	if err != nil {
+		return 0, errors.Wrap(err, "opening data subdirectory")
+	}
+	defer dir.Close()
+
+	files, err := dir.Readdir(-1)
+	if err != nil {
+		return 0, errors.Wrap(err, "reading data subdirectory")
+	}
+
+	for _, file := range files {
+		if file.IsDir() {
+			sz, err := directoryUsage(path.Join(fname, file.Name()))
+			if err != nil {
+				return 0, err
+			}
+			size += sz
+		} else {
+			size += file.Size()
+		}
+	}
+
+	return size, nil
+}
+
 func (f *TxFactory) CloseIndex(idx *Index) error {
 	// under roaring and all the new databases, this is a no-op.
 	//idx.Dump("CloseIndex")