diff --git a/fs_mgr/libsnapshot/snapshot_writer.cpp b/fs_mgr/libsnapshot/snapshot_writer.cpp
index 6aad3d1..82a7fd7 100644
--- a/fs_mgr/libsnapshot/snapshot_writer.cpp
+++ b/fs_mgr/libsnapshot/snapshot_writer.cpp
@@ -93,6 +93,9 @@
 
 std::unique_ptr<FileDescriptor> CompressedSnapshotWriter::OpenReader() {
     auto cow = OpenCowReader();
+    if (cow == nullptr) {
+        return nullptr;
+    }
 
     auto reader = std::make_unique<CompressedSnapshotReader>();
     if (!reader->SetCow(std::move(cow))) {
diff --git a/rootdir/init.rc b/rootdir/init.rc
index f05c0bf..1131f3f 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -1108,6 +1108,7 @@
     # are not aware of using fsync()/sync() to prepare sudden power-cut.
     write /dev/sys/fs/by-name/userdata/cp_interval 200
     write /dev/sys/fs/by-name/userdata/gc_urgent_sleep_time 50
+    write /dev/sys/fs/by-name/userdata/iostat_period_ms 1000
     write /dev/sys/fs/by-name/userdata/iostat_enable 1
 
     # set readahead multiplier for POSIX_FADV_SEQUENTIAL files