diff --git a/swh/objstorage/backends/pathslicing.py b/swh/objstorage/backends/pathslicing.py
--- a/swh/objstorage/backends/pathslicing.py
+++ b/swh/objstorage/backends/pathslicing.py
@@ -57,6 +57,11 @@
     with gzip.GzipFile(filename=tmp_path, fileobj=tmp_f) as f:
         yield f
 
+    # Make sure the contents of the temporary file are written to disk
+    tmp_f.flush()
+    if objstorage.use_fdatasync:
+        os.fdatasync(tmp)
+
     # Then close the temporary file and move it to the right directory.
     tmp_f.close()
     os.chmod(tmp_path, FILE_MODE)
@@ -126,6 +131,8 @@
             if sbounds
         ]
 
+        self.use_fdatasync = hasattr(os, 'fdatasync')
+
         self.check_config(check_write=False)
 
     def check_config(self, *, check_write):
diff --git a/swh/objstorage/tests/test_objstorage_pathslicing.py b/swh/objstorage/tests/test_objstorage_pathslicing.py
--- a/swh/objstorage/tests/test_objstorage_pathslicing.py
+++ b/swh/objstorage/tests/test_objstorage_pathslicing.py
@@ -6,6 +6,7 @@
 import shutil
 import tempfile
 import unittest
+from unittest.mock import patch
 import gzip
 
 from swh.model import hashutil
@@ -109,3 +110,26 @@
         self.assertEqual(n_leaf, 2)  # beware, this depends on the hash algo
         self.assertEqual(len(ids), 1)
         self.assertEqual(ids, all_ids[-1:])
+
+    def test_fdatasync_default(self):
+        content, obj_id = self.hash_content(b'check_fdatasync')
+        with patch('os.fdatasync') as mock_fdatasync:
+            self.storage.add(content, obj_id=obj_id)
+        if self.storage.use_fdatasync:
+            mock_fdatasync.assert_called_once()
+        else:
+            mock_fdatasync.assert_not_called()
+
+    def test_fdatasync_forced_on(self):
+        self.storage.use_fdatasync = True
+        content, obj_id = self.hash_content(b'check_fdatasync')
+        with patch('os.fdatasync') as mock_fdatasync:
+            self.storage.add(content, obj_id=obj_id)
+        mock_fdatasync.assert_called_once()
+
+    def test_fdatasync_forced_off(self):
+        self.storage.use_fdatasync = False
+        content, obj_id = self.hash_content(b'check_fdatasync')
+        with patch('os.fdatasync') as mock_fdatasync:
+            self.storage.add(content, obj_id=obj_id)
+        mock_fdatasync.assert_not_called()