diff --git a/internal/datamanager/data.go b/internal/datamanager/data.go
index d100843..7c790c6 100644
--- a/internal/datamanager/data.go
+++ b/internal/datamanager/data.go
@@ -89,7 +89,7 @@ func (d *DataManager) writeData(ctx context.Context, wals []*WalData) error {
 	if err != nil {
 		return err
 	}
-	if err := d.ost.WriteObject(dataStatusPath(dataSequence.String()), bytes.NewReader(dataStatusj)); err != nil {
+	if err := d.ost.WriteObject(dataStatusPath(dataSequence.String()), bytes.NewReader(dataStatusj), true); err != nil {
 		return err
 	}
 
@@ -203,7 +203,7 @@ func (d *DataManager) writeDataType(ctx context.Context, wals []*WalData, dataty
 
 		pos += len(dataEntryj)
 	}
-	if err := d.ost.WriteObject(dataFilePath(datatype, dataSequence), &buf); err != nil {
+	if err := d.ost.WriteObject(dataFilePath(datatype, dataSequence), &buf, true); err != nil {
 		return err
 	}
 
@@ -211,7 +211,7 @@ func (d *DataManager) writeDataType(ctx context.Context, wals []*WalData, dataty
 	if err != nil {
 		return err
 	}
-	if err := d.ost.WriteObject(dataFileIndexPath(datatype, dataSequence), bytes.NewReader(dataFileIndexj)); err != nil {
+	if err := d.ost.WriteObject(dataFileIndexPath(datatype, dataSequence), bytes.NewReader(dataFileIndexj), true); err != nil {
 		return err
 	}
 
diff --git a/internal/datamanager/wal.go b/internal/datamanager/wal.go
index 8dff9d6..1290cba 100644
--- a/internal/datamanager/wal.go
+++ b/internal/datamanager/wal.go
@@ -485,7 +485,7 @@ func (d *DataManager) WriteWalAdditionalOps(ctx context.Context, actions []*Acti
 			return nil, err
 		}
 	}
-	if err := d.ost.WriteObject(walDataFilePath, bytes.NewReader(buf.Bytes())); err != nil {
+	if err := d.ost.WriteObject(walDataFilePath, bytes.NewReader(buf.Bytes()), true); err != nil {
 		return nil, err
 	}
 	d.log.Debugf("wrote wal file: %s", walDataFilePath)
@@ -629,7 +629,7 @@ func (d *DataManager) sync(ctx context.Context) error {
 			}
 
 			walFileCommittedPath := walFilePath + ".committed"
-			if err := d.ost.WriteObject(walFileCommittedPath, bytes.NewReader(headerj)); err != nil {
+			if err := d.ost.WriteObject(walFileCommittedPath, bytes.NewReader(headerj), true); err != nil {
 				return err
 			}
 
@@ -659,7 +659,7 @@ func (d *DataManager) sync(ctx context.Context) error {
 			walFilePath := d.storageWalStatusFile(walData.WalSequence)
 			d.log.Debugf("checkpointing committed wal to storage")
 			walFileCheckpointedPath := walFilePath + ".checkpointed"
-			if err := d.ost.WriteObject(walFileCheckpointedPath, bytes.NewReader([]byte{})); err != nil {
+			if err := d.ost.WriteObject(walFileCheckpointedPath, bytes.NewReader([]byte{}), true); err != nil {
 				return err
 			}
 		}
diff --git a/internal/objectstorage/objectstorage.go b/internal/objectstorage/objectstorage.go
index 69ebd5b..eb5c996 100644
--- a/internal/objectstorage/objectstorage.go
+++ b/internal/objectstorage/objectstorage.go
@@ -35,7 +35,7 @@ type ReadSeekCloser interface {
 type Storage interface {
 	Stat(filepath string) (*ObjectInfo, error)
 	ReadObject(filepath string) (ReadSeekCloser, error)
-	WriteObject(filepath string, data io.Reader) error
+	WriteObject(filepath string, data io.Reader, persist bool) error
 	DeleteObject(filepath string) error
 	List(prefix, startWith, delimiter string, doneCh <-chan struct{}) <-chan ObjectInfo
 }
diff --git a/internal/objectstorage/objectstorage_test.go b/internal/objectstorage/objectstorage_test.go
index 8590cf1..667d7e2 100644
--- a/internal/objectstorage/objectstorage_test.go
+++ b/internal/objectstorage/objectstorage_test.go
@@ -260,7 +260,7 @@ func TestList(t *testing.T) {
 				os := NewObjStorage(s, "/")
 				// populate
 				for _, p := range tt.objects {
-					if err := os.WriteObject(p, strings.NewReader("")); err != nil {
+					if err := os.WriteObject(p, strings.NewReader(""), true); err != nil {
 						t.Fatalf("%s %d err: %v", sname, i, err)
 					}
 				}
diff --git a/internal/objectstorage/posix.go b/internal/objectstorage/posix.go
index aa51be1..5a3e5ff 100644
--- a/internal/objectstorage/posix.go
+++ b/internal/objectstorage/posix.go
@@ -264,7 +264,7 @@ func (s *PosixStorage) ReadObject(p string) (ReadSeekCloser, error) {
 	return f, err
 }
 
-func (s *PosixStorage) WriteObject(p string, data io.Reader) error {
+func (s *PosixStorage) WriteObject(p string, data io.Reader, persist bool) error {
 	fspath, err := s.fsPath(p)
 	if err != nil {
 		return err
@@ -273,7 +273,7 @@ func (s *PosixStorage) WriteObject(p string, data io.Reader) error {
 	if err := os.MkdirAll(path.Dir(fspath), 0770); err != nil {
 		return err
 	}
-	return s.WriteFileAtomicFunc(fspath, 0660, func(f io.Writer) error {
+	return s.WriteFileAtomicFunc(fspath, 0660, persist, func(f io.Writer) error {
 		_, err := io.Copy(f, data)
 		return err
 	})
@@ -437,13 +437,13 @@ func (s *PosixStorage) List(prefix, startWith, delimiter string, doneCh <-chan s
 // data to the file.
 // TODO(sgotti) remove left over tmp files if process crashes before calling
 // os.Remove
-func (s *PosixStorage) WriteFileAtomicFunc(p string, perm os.FileMode, writeFunc func(f io.Writer) error) error {
+func (s *PosixStorage) WriteFileAtomicFunc(p string, perm os.FileMode, persist bool, writeFunc func(f io.Writer) error) error {
 	f, err := ioutil.TempFile(s.tmpDir, "tmpfile")
 	if err != nil {
 		return err
 	}
 	err = writeFunc(f)
-	if err == nil {
+	if persist && err == nil {
 		err = f.Sync()
 	}
 	if closeErr := f.Close(); err == nil {
@@ -460,6 +460,9 @@ func (s *PosixStorage) WriteFileAtomicFunc(p string, perm os.FileMode, writeFunc
 		return err
 	}
 
+	if !persist {
+		return nil
+	}
 	// sync parent dirs
 	pdir := filepath.Dir(p)
 	for {
@@ -482,8 +485,8 @@ func (s *PosixStorage) WriteFileAtomicFunc(p string, perm os.FileMode, writeFunc
 	return nil
 }
 
-func (s *PosixStorage) WriteFileAtomic(filename string, perm os.FileMode, data []byte) error {
-	return s.WriteFileAtomicFunc(filename, perm,
+func (s *PosixStorage) WriteFileAtomic(filename string, perm os.FileMode, persist bool, data []byte) error {
+	return s.WriteFileAtomicFunc(filename, perm, persist,
 		func(f io.Writer) error {
 			_, err := f.Write(data)
 			return err
diff --git a/internal/objectstorage/posix_test.go b/internal/objectstorage/posix_test.go
index fe256e4..7787532 100644
--- a/internal/objectstorage/posix_test.go
+++ b/internal/objectstorage/posix_test.go
@@ -92,7 +92,7 @@ func TestDeleteObject(t *testing.T) {
 	}
 
 	for _, obj := range objects {
-		if err := ls.WriteObject(obj, bytes.NewReader([]byte{})); err != nil {
+		if err := ls.WriteObject(obj, bytes.NewReader([]byte{}), true); err != nil {
 			t.Fatalf("unexpected err: %v", err)
 		}
 		if err := ls.DeleteObject(obj); err != nil {
diff --git a/internal/objectstorage/s3.go b/internal/objectstorage/s3.go
index 1be8f81..303acf8 100644
--- a/internal/objectstorage/s3.go
+++ b/internal/objectstorage/s3.go
@@ -84,7 +84,7 @@ func (s *S3Storage) ReadObject(filepath string) (ReadSeekCloser, error) {
 	return s.minioClient.GetObject(s.bucket, filepath, minio.GetObjectOptions{})
 }
 
-func (s *S3Storage) WriteObject(filepath string, data io.Reader) error {
+func (s *S3Storage) WriteObject(filepath string, data io.Reader, persist bool) error {
 	// hack to know the real file size or minio will do this in memory with big memory usage since s3 doesn't support real streaming of unknown sizes
 	// TODO(sgotti) wait for minio client to expose an api to provide the max part size so we can remove this
 	tmpfile, err := ioutil.TempFile(os.TempDir(), "s3")
diff --git a/internal/services/runservice/scheduler/api/executor.go b/internal/services/runservice/scheduler/api/executor.go
index 233ace4..deab9ab 100644
--- a/internal/services/runservice/scheduler/api/executor.go
+++ b/internal/services/runservice/scheduler/api/executor.go
@@ -411,7 +411,7 @@ func (h *CacheCreateHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	cachePath := store.OSTCachePath(key)
-	if err := h.ost.WriteObject(cachePath, r.Body); err != nil {
+	if err := h.ost.WriteObject(cachePath, r.Body, false); err != nil {
 		http.Error(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
diff --git a/internal/services/runservice/scheduler/scheduler.go b/internal/services/runservice/scheduler/scheduler.go
index c46f220..0ad45b5 100644
--- a/internal/services/runservice/scheduler/scheduler.go
+++ b/internal/services/runservice/scheduler/scheduler.go
@@ -931,7 +931,7 @@ func (s *Scheduler) fetchLog(ctx context.Context, rt *types.RunTask, setup bool,
 		return errors.Errorf("received http status: %d", r.StatusCode)
 	}
 
-	return s.ost.WriteObject(logPath, r.Body)
+	return s.ost.WriteObject(logPath, r.Body, false)
 }
 
 func (s *Scheduler) finishSetupLogPhase(ctx context.Context, runID, runTaskID string) error {
@@ -1073,7 +1073,7 @@ func (s *Scheduler) fetchArchive(ctx context.Context, rt *types.RunTask, stepnum
 		return errors.Errorf("received http status: %d", r.StatusCode)
 	}
 
-	return s.ost.WriteObject(path, r.Body)
+	return s.ost.WriteObject(path, r.Body, false)
 }
 
 func (s *Scheduler) fetchTaskArchives(ctx context.Context, runID string, rt *types.RunTask) {