diff --git a/dpdispatcher/ssh_context.py b/dpdispatcher/ssh_context.py
index 1c00fdf1..771609cd 100644
--- a/dpdispatcher/ssh_context.py
+++ b/dpdispatcher/ssh_context.py
@@ -169,10 +169,12 @@ class SSHContext (object):
     def __init__ (self,
                 local_root,
                 ssh_session,
+                clean_asynchronously=False,
                 ):
         assert(type(local_root) == str)
         self.temp_local_root = os.path.abspath(local_root)
         self.job_uuid = None
+        self.clean_asynchronously = clean_asynchronously
         # self.job_uuid = job_uuid
         # if job_uuid:
         #    self.job_uuid=job_uuid
@@ -203,7 +205,8 @@ def from_jdata(cls, jdata):
         ssh_session = SSHSession(**input)
         ssh_context = SSHContext(
             local_root=local_root,
-            ssh_session=ssh_session
+            ssh_session=ssh_session,
+            clean_asynchronously=jdata.get('clean_asynchronously', False),
             )
         return ssh_context
     
@@ -296,8 +299,11 @@ def download(self,
         
     def block_checkcall(self, 
                         cmd,
+                        asynchronously=False,
                         retry=0) :
         self.ssh_session.ensure_alive()
+        if asynchronously:
+            cmd = "nohup %s >/dev/null &" % cmd
         stdin, stdout, stderr = self.ssh_session.exec_command(('cd %s ;' % self.remote_root) + cmd)
         exit_status = stdout.channel.recv_exit_status() 
         if exit_status != 0:
@@ -307,7 +313,7 @@ def block_checkcall(self,
                         (exit_status, cmd, self.job_uuid, stderr.read().decode('utf-8')))
                 dlog.warning("Sleep 60 s and retry the command...")
                 time.sleep(60)
-                return self.block_checkcall(cmd, retry=retry+1)
+                return self.block_checkcall(cmd, asynchronously=asynchronously, retry=retry+1)
             print('debug:self.remote_root, cmd', self.remote_root, cmd)
             raise RuntimeError("Get error code %d in calling %s through ssh with job: %s . message: %s" %
                                (exit_status, cmd, self.job_uuid, stderr.read().decode('utf-8')))
@@ -322,7 +328,7 @@ def block_call(self,
 
     def clean(self) :        
         self.ssh_session.ensure_alive()
-        self.sftp._rmtree(sftp, self.remote_root)
+        self._rmtree(self.remote_root)
 
     def write_file(self, fname, write_str):
         self.ssh_session.ensure_alive()
@@ -367,17 +373,18 @@ def kill(self, cmd_pipes) :
         self.block_checkcall('kill -15 %s' % cmd_pipes['pid'])
 
 
-    def _rmtree(self, sftp, remotepath, level=0, verbose = False):
-        for f in sftp.listdir_attr(remotepath):
-            rpath = os.path.join(remotepath, f.filename)
-            if stat.S_ISDIR(f.st_mode):
-                self._rmtree(sftp, rpath, level=(level + 1))
-            else:
-                rpath = os.path.join(remotepath, f.filename)
-                if verbose: dlog.info('removing %s%s' % ('    ' * level, rpath))
-                sftp.remove(rpath)
-        if verbose: dlog.info('removing %s%s' % ('    ' * level, remotepath))
-        sftp.rmdir(remotepath)
+    def _rmtree(self, remotepath, verbose = False):
+        """Remove the remote path."""
+        # The original implementation method removes files one by one using sftp.
+        # If the latency of the remote server is high, it is very slow.
+        # Thus, it's better to use system's `rm` to remove a directory, which may
+        # save a lot of time.
+        if verbose:
+            dlog.info('removing %s' % remotepath)
+        # In some supercomputers, it's very slow to remove large numbers of files
+        # (e.g. directory containing trajectory) due to bad I/O performance.
+        # So an asynchronously option is provided.
+        self.block_checkcall('rm -rf %s' % remotepath, asynchronously=self.clean_asynchronously)
 
     def _put_files(self,
                    files,