[Samba] How many memory do I need with the samba4 dc?

[Sense Zeng]

My samba version is 4.1.3 and self compiled. My AD is running with win2003
DC.
I'm now use a server with 4G ram to join as DC. It's seams can run with use
4G more swap. But I have other problem. I run twice, after about 6 hour,
samba-tool domain join stop. Folow is some info:

Command:
samba-tool domain join mydomain.local DC
-Uadministrator at MYDOMAIN.LOCAL--server=win2003dc.mydomain.local
--realm=mydomain.local
--dns-backend=BIND9_DLZ

6h it stoped. Err message:
...
Partition[DC=gdsyzx,DC=edu,DC=cn] objects[222918] linked_values[0]
Done with always replicated NC (base, config, schema)
Replicating DC=DomainDnsZones,DC=gdsyzx,DC=edu,DC=cn
Join failed - cleaning up
checking sAMAccountName
ERROR(runtime): uncaught exception - (-1073741643, 'NT_STATUS_IO_TIMEOUT')
  File
"/usr/local/samba/lib/python2.7/site-packages/samba/netcmd/__init__.py",
line 175, in _run
    return self.run(*args, **kwargs)
  File
"/usr/local/samba/lib/python2.7/site-packages/samba/netcmd/domain.py", line
552, in run
    machinepass=machinepass, use_ntvfs=use_ntvfs, dns_backend=dns_backend)
  File "/usr/local/samba/lib/python2.7/site-packages/samba/join.py", line
1172, in join_DC
    ctx.do_join()
  File "/usr/local/samba/lib/python2.7/site-packages/samba/join.py", line
1077, in do_join
    ctx.join_replicate()
  File "/usr/local/samba/lib/python2.7/site-packages/samba/join.py", line
825, in join_replicate
    replica_flags=ctx.replica_flags)
  File "/usr/local/samba/lib/python2.7/site-packages/samba/drs_utils.py",
line 252, in replicate
    (level, ctr) = self.drs.DsGetNCChanges(self.drs_handle, req_level, req)