diff --git a/go.mod b/go.mod
index 5a3cdd5..945846d 100644
--- a/go.mod
+++ b/go.mod
@@ -9,6 +9,7 @@ require (
 	github.com/lib/pq v1.10.6
 	github.com/pkg/errors v0.9.1
 	github.com/shopspring/decimal v1.3.1 // indirect
+	github.com/stretchr/testify v1.7.0
 	golang.org/x/crypto v0.0.0-20220517005047-85d78b3ac167 // indirect
 	golang.org/x/sys v0.0.0-20220513210249-45d2b4557a2a // indirect
 	gorm.io/driver/postgres v1.3.5
diff --git a/testserver/testserver.go b/testserver/testserver.go
index fda4c1e..0ad4ced 100644
--- a/testserver/testserver.go
+++ b/testserver/testserver.go
@@ -18,22 +18,23 @@
 // from your PATH.
 //
 // To use, run as follows:
-//   import "github.com/cockroachdb/cockroach-go/v2/testserver"
-//   import "testing"
-//   import "time"
 //
-//   func TestRunServer(t *testing.T) {
-//      ts, err := testserver.NewTestServer()
-//      if err != nil {
-//        t.Fatal(err)
-//      }
-//      defer ts.Stop()
+//	import "github.com/cockroachdb/cockroach-go/v2/testserver"
+//	import "testing"
+//	import "time"
 //
-//      db, err := sql.Open("postgres", ts.PGURL().String())
-//      if err != nil {
-//        t.Fatal(err)
-//      }
-//    }
+//	func TestRunServer(t *testing.T) {
+//	   ts, err := testserver.NewTestServer()
+//	   if err != nil {
+//	     t.Fatal(err)
+//	   }
+//	   defer ts.Stop()
+//
+//	   db, err := sql.Open("postgres", ts.PGURL().String())
+//	   if err != nil {
+//	     t.Fatal(err)
+//	   }
+//	 }
 package testserver
 
 import (
@@ -222,6 +223,7 @@ type testServerArgs struct {
 	cockroachBinary        string // path to cockroach executable file
 	upgradeCockroachBinary string // path to cockroach binary for upgrade
 	numNodes               int
+	externalIODir          string
 }
 
 // CockroachBinaryPathOpt is a TestServer option that can be passed to
@@ -330,6 +332,14 @@ func ThreeNodeOpt() TestServerOpt {
 	}
 }
 
+// ExternalIODirOpt is a TestServer option that can be passed to NewTestServer to
+// specify the external IO directory to be used for the cluster.
+func ExternalIODirOpt(ioDir string) TestServerOpt {
+	return func(args *testServerArgs) {
+		args.externalIODir = ioDir
+	}
+}
+
 const (
 	logsDirName  = "logs"
 	certsDirName = "certs"
@@ -489,6 +499,10 @@ func NewTestServer(opts ...TestServerOpt) (TestServer, error) {
 		serverArgs.httpPorts = make([]int, serverArgs.numNodes)
 	}
 
+	if serverArgs.externalIODir == "" {
+		serverArgs.externalIODir = "disabled"
+	}
+
 	for i := 0; i < serverArgs.numNodes; i++ {
 		nodes[i].state = stateNew
 		nodes[i].listeningURLFile = filepath.Join(baseDir, fmt.Sprintf("listen-url%d", i))
@@ -503,6 +517,7 @@ func NewTestServer(opts ...TestServerOpt) (TestServer, error) {
 				fmt.Sprintf("--http-addr=localhost:%d", serverArgs.httpPorts[i]),
 				"--listening-url-file=" + nodes[i].listeningURLFile,
 				joinArg,
+				"--external-io-dir=" + serverArgs.externalIODir,
 			}
 		} else {
 			nodes[0].startCmdArgs = []string{
@@ -515,6 +530,7 @@ func NewTestServer(opts ...TestServerOpt) (TestServer, error) {
 				"--http-port=" + strconv.Itoa(serverArgs.httpPorts[0]),
 				storeArg,
 				"--listening-url-file=" + nodes[i].listeningURLFile,
+				"--external-io-dir=" + serverArgs.externalIODir,
 			}
 		}
 	}
diff --git a/testserver/testserver_test.go b/testserver/testserver_test.go
index 583706c..e69ad86 100644
--- a/testserver/testserver_test.go
+++ b/testserver/testserver_test.go
@@ -252,6 +252,29 @@ func TestCockroachBinaryPathOpt(t *testing.T) {
 	}
 }
 
+func TestCockroachExternalIODirOpt(t *testing.T) {
+	externalDir, err := os.MkdirTemp("/tmp", "cockroach-testserver")
+	require.NoError(t, err)
+	defer func() {
+		err := os.RemoveAll(externalDir)
+		require.NoError(t, err)
+	}()
+
+	db, cleanup := testserver.NewDBForTest(t, testserver.ExternalIODirOpt(externalDir))
+	defer cleanup()
+
+	// test that we can use external dir
+	_, err = db.Exec("BACKUP INTO 'nodelocal://self/backup'")
+	require.NoError(t, err)
+
+	// test that external dir has files
+	f, err := os.Open(externalDir)
+	require.NoError(t, err)
+	defer f.Close()
+	_, err = f.Readdirnames(1)
+	require.NoError(t, err)
+}
+
 func TestPGURLWhitespace(t *testing.T) {
 	ts, err := testserver.NewTestServer()
 	if err != nil {