We have 2 running s4 DCs in production (migrated from s3), more than half thousand users. From time to time (after some changes are made to the directory, e.g. group policies) I see these messages in the logs (log level = 2): [2012/11/12 09:23:00, 0] ../source4/rpc_server/common/forward.c:51(dcesrv_irpc_forward_callback) IRPC callback failed for DsReplicaSync - NT_STATUS_IO_TIMEOUT [2012/11/12 09:23:00, 2] default/librpc/gen_ndr/ndr_drsuapi_s.c:394(drsuapi__op_reply) dcerpc_fault WERR_EPT_S_CANT_PERFORM_OP in drsuapi_DsReplicaSync The same time on the other DC I see repeating messages (as I understand it's trying to replicate, but fails): [2012/11/12 09:22:41, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on DC=domain,DC=ru using filter (uSNChanged>=13902) [2012/11/12 09:22:41, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 13902 flags 0x00000074 on <GUID=81116378-3e99-4d1f-804d-8a8925f3dd55>;<SID=S-1-5-21-530720856-2058831417-1234567890>;DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:42, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on DC=ForestDnsZones,DC=domain,DC=ru using filter (uSNChanged>=5133) [2012/11/12 09:22:42, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 5133 flags 0x00000074 on <GUID=8296a94f-d92b-4ee5-8687-deebc22b0f92>;DC=ForestDnsZones,DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:42, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on DC=DomainDnsZones,DC=domain,DC=ru using filter (uSNChanged>=5115) [2012/11/12 09:22:42, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 5115 flags 0x00000074 on <GUID=76fd0afd-cc86-4d23-b7c6-3f9671c244ff>;DC=DomainDnsZones,DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:43, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on DC=domain,DC=ru using filter (uSNChanged>=13902) [2012/11/12 09:22:43, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 13902 flags 0x00000074 on <GUID=81116378-3e99-4d1f-804d-8a8925f3dd55>;<SID=S-1-5-21-530720856-2058831417-1234567890>;DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:43, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on CN=Schema,CN=Configuration,DC=domain,DC=ru using filter (uSNChanged>=1558) [2012/11/12 09:22:43, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 1558 flags 0x00000074 on <GUID=affe8535-a031-4a34-8356-7b94cfbe1291>;CN=Schema,CN=Configuration,DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:44, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on CN=Configuration,DC=domain,DC=ru using filter (uSNChanged>=12907) [2012/11/12 09:22:44, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 12907 flags 0x00000074 on <GUID=76a7c9b6-0b25-48a4-b85f-a9e57c14b0ad>;CN=Configuration,DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:49, 2] ../source4/smbd/process_standard.c:197(standard_terminate) standard_terminate: reason[NT_STATUS_END_OF_FILE] [2012/11/12 09:22:51, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on DC=domain,DC=ru using filter (uSNChanged>=13902) [2012/11/12 09:22:51, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 13902 flags 0x00000074 on <GUID=81116378-3e99-4d1f-804d-8a8925f3dd55>;<SID=S-1-5-21-530720856-2058831417-1234567890>;DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:52, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on DC=ForestDnsZones,DC=domain,DC=ru using filter (uSNChanged>=5133) [2012/11/12 09:22:52, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 5133 flags 0x00000074 on <GUID=8296a94f-d92b-4ee5-8687-deebc22b0f92>;DC=ForestDnsZones,DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:52, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on DC=DomainDnsZones,DC=domain,DC=ru using filter (uSNChanged>=5115) [2012/11/12 09:22:52, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 5115 flags 0x00000074 on <GUID=76fd0afd-cc86-4d23-b7c6-3f9671c244ff>;DC=DomainDnsZones,DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:53, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on DC=domain,DC=ru using filter (uSNChanged>=13902) [2012/11/12 09:22:53, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 13902 flags 0x00000074 on <GUID=81116378-3e99-4d1f-804d-8a8925f3dd55>;<SID=S-1-5-21-530720856-2058831417-1234567890>;DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:53, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on CN=Schema,CN=Configuration,DC=domain,DC=ru using filter (uSNChanged>=1558) [2012/11/12 09:22:54, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 1558 flags 0x00000074 on <GUID=affe8535-a031-4a34-8356-7b94cfbe1291>;CN=Schema,CN=Configuration,DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:22:54, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on CN=Configuration,DC=domain,DC=ru using filter (uSNChanged>=12907) [2012/11/12 09:22:54, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 12907 flags 0x00000074 on <GUID=76a7c9b6-0b25-48a4-b85f-a9e57c14b0ad>;CN=Configuration,DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:23:00, 2] ../source4/smbd/process_standard.c:197(standard_terminate) standard_terminate: reason[NT_STATUS_END_OF_FILE] [2012/11/12 09:23:01, 2] ../source4/rpc_server/drsuapi/getncchanges.c:1395(getncchanges_collect_objects) ../source4/rpc_server/drsuapi/getncchanges.c:1395: getncchanges on DC=domain,DC=ru using filter (uSNChanged>=13902) [2012/11/12 09:23:01, 2] ../source4/rpc_server/drsuapi/getncchanges.c:2007(dcesrv_drsuapi_DsGetNCChanges) DsGetNCChanges with uSNChanged >= 13902 flags 0x00000074 on <GUID=81116378-3e99-4d1f-804d-8a8925f3dd55>;<SID=S-1-5-21-530720856-2058831417-1234567890>;DC=domain,DC=ru gave 0 objects (done 0/0) 0 links (done 0/0 (as S-1-5-21-530720856-2058831417-1234567890-7087)) [2012/11/12 09:23:02, 2] ../source4/smbd/process_standard.c:197(standard_terminate) standard_terminate: reason[NT_STATUS_END_OF_FILE] And it's repeating until I restart samba on the first DC (I have a cronjob for this on both DCs as a dirty workaround). After restarting all is ok, until something (don't know what exactly) is changed in the directory again. samba-tool dbcheck doesn't find anything wrong. What additional info could help here? Because of the restarting - this issue is really critical for us, I'll be glad if you help me with this. # samba --version Version 4.1.0pre1-GIT-50d47fc # uname -a Linux dc0 3.2.0-32-generic #51-Ubuntu SMP Wed Sep 26 21:33:09 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux