1045:
38:
101:. If the malfunctioning node is really down, then it cannot do any damage, so theoretically no action would be required (it could simply be brought back into the cluster with the usual join process). However, because there is a possibility that a malfunctioning node could itself consider the rest of the cluster to be the one that is malfunctioning, a
117:
There are two classes of fencing methods, one which disables a node itself, the other disallows access to resources such as shared disks. In some cases, it is assumed that if a node does not respond after a given time-threshold it may be assumed as non-operational, although there are counterexamples,
65:
As the number of nodes in a cluster increases, so does the likelihood that one of them may fail at some point. The failed node may have control over shared resources that need to be reclaimed and if the node is acting erratically, the rest of the system needs to be protected. Fencing may thus either
173:
Persistent reservation is essentially a match on a key, so the node which has the right key can do I/O, otherwise its I/O fails. Therefore, it is sufficient to change the key on a failure to ensure the right behavior during failure. However, it may not always be possible to change the key on the
74:
A node fence (or I/O fence) is a virtual "fence" that separates nodes which must not have access to a shared resource from that resource. It may separate an active node from its backup. If the backup crosses the fence and, for example, tries to control the same disk array as the primary, a data
169:
When the cluster has only two nodes, the reserve/release method may be used as a two node STONITH whereby upon detecting that node B has 'failed', node A will issue the reserve and obtain all resources (e.g. shared disk) for itself. Node B will be disabled if it tries to do I/O (in case it was
129:
uses a power controller to turn off an inoperable node. The node may then restart itself and join the cluster later. However, there are approaches in which an operator is informed of the need for a manual restart for the node.
177:
STONITH is an easier and simpler method to implement on multiple clusters, while the various approaches to resources fencing require specific implementation approaches for each cluster implementation.
281:
94:
from other active nodes modifying the resources during node failures. Mechanisms to support fencing, such as the reserve/release mechanism of SCSI, have existed since at least 1985.
371:
461:
220:
313:
1075:
442:
709:
732:
621:
727:
704:
306:
125:
method stands for "Shoot The Other Node In The Head", meaning that the suspected node is disabled or powered off. For instance,
699:
514:
806:
669:
1030:
864:
482:
402:
1049:
995:
455:
299:
160:
45:
231:
1070:
974:
769:
654:
616:
466:
356:
990:
969:
914:
801:
791:
764:
626:
286:
944:
570:
509:
422:
859:
1005:
1000:
450:
102:
87:
744:
676:
580:
472:
427:
86:
can no longer be done from it. Fencing is typically done automatically, by cluster infrastructure such as
534:
836:
796:
749:
739:
477:
397:
336:
776:
664:
659:
649:
636:
432:
939:
894:
720:
715:
694:
560:
97:
Fencing is required because it is impossible to distinguish between a real failure and a temporary
91:
964:
813:
786:
611:
575:
565:
366:
346:
341:
322:
524:
1010:
686:
644:
539:
55:
109:. Instead, the system has to assume the worst scenario and always fence in case of problems.
1020:
819:
754:
601:
417:
412:
407:
376:
98:
59:
884:
824:
759:
606:
596:
529:
361:
351:
186:
106:
519:
137:
approach disallows access to resources without powering off the node. This may include:
1015:
831:
488:
381:
28:
260:
1064:
904:
781:
154:
504:
170:
temporarily hung). On node B the I/O failure triggers some code to kill the node.
66:
disable the node, or disallow shared storage access, thus ensuring data integrity.
1025:
899:
874:
17:
62:
or protecting shared resources when a node appears to be malfunctioning.
949:
929:
854:
191:
37:
954:
934:
909:
544:
122:
76:
924:
919:
291:
147:
36:
282:
Red Hat GFS 6.0: Administrator's Guide - Using the
Fencing System
959:
889:
879:
250:
by
Enrique Vargas, Joseph Bianco, David Deeths 2001 ISBN page 58
295:
869:
846:
83:
42:
150:
persistent reservations to block access to shared storage.
163:(GNBD) fencing which disables access to the GNBD server
983:
845:
685:
635:
589:
553:
497:
441:
390:
329:
221:"Alan Robertson Resource fencing using STONITH"
34:Isolation of malfunctioning computer resources
307:
8:
314:
300:
292:
248:Sun Cluster environment: Sun Cluster 2.2
79:are designed to prevent this condition.
203:
215:
213:
211:
209:
207:
82:Isolating a node means ensuring that
75:hazard may occur. Mechanisms such as
7:
261:"Small Computer Standards Interface"
153:Fibre Channel fencing disables the
25:
1044:
1043:
1076:Fault-tolerant computer systems
515:Analysis of parallel algorithms
287:OCFS2 FAQ - Quorum and fencing
144:Persistent reservation fencing
54:is the process of isolating a
1:
462:Simultaneous and heterogenous
1050:Category: Parallel computing
118:e.g. a long paging rampage.
161:Global network block device
1092:
357:High-performance computing
26:
1039:
991:Automatic parallelization
627:Application checkpointing
228:IBM Linux Research Center
88:shared disk file systems
27:Not to be confused with
1006:Embarrassingly parallel
1001:Deterministic algorithm
105:could ensue, and cause
721:Associative processing
677:Non-blocking algorithm
483:Clustered multi-thread
90:, in order to protect
48:
837:Hardware acceleration
750:Superscalar processor
740:Dataflow architecture
337:Distributed computing
113:Approaches to fencing
103:split brain condition
40:
716:Pipelined processing
665:Explicit parallelism
660:Implicit parallelism
650:Dataflow programming
940:Parallel Extensions
745:Pipelined processor
814:Massively parallel
792:distributed shared
612:Cache invalidation
576:Instruction window
367:Manycore processor
347:Massively parallel
342:Parallel computing
323:Parallel computing
49:
1071:Cluster computing
1058:
1057:
1011:Parallel slowdown
645:Stream processing
535:Karp–Flatt metric
135:resources fencing
16:(Redirected from
1083:
1047:
1046:
1021:Software lockout
820:Computer cluster
755:Vector processor
710:Array processing
695:Flynn's taxonomy
602:Memory coherence
377:Computer network
316:
309:
302:
293:
269:
268:
265:ANSI X3.131-1986
257:
251:
245:
239:
238:
236:
230:. Archived from
225:
217:
60:computer cluster
21:
1091:
1090:
1086:
1085:
1084:
1082:
1081:
1080:
1061:
1060:
1059:
1054:
1035:
979:
885:Coarray Fortran
841:
825:Beowulf cluster
681:
631:
622:Synchronization
607:Cache coherence
597:Multiprocessing
585:
549:
530:Cost efficiency
525:Gustafson's law
493:
437:
386:
362:Multiprocessing
352:Cloud computing
325:
320:
278:
273:
272:
259:
258:
254:
246:
242:
234:
223:
219:
218:
205:
200:
187:Fault tolerance
183:
115:
107:data corruption
72:
46:Nehalem cluster
35:
32:
23:
22:
15:
12:
11:
5:
1089:
1087:
1079:
1078:
1073:
1063:
1062:
1056:
1055:
1053:
1052:
1040:
1037:
1036:
1034:
1033:
1028:
1023:
1018:
1016:Race condition
1013:
1008:
1003:
998:
993:
987:
985:
981:
980:
978:
977:
972:
967:
962:
957:
952:
947:
942:
937:
932:
927:
922:
917:
912:
907:
902:
897:
892:
887:
882:
877:
872:
867:
862:
857:
851:
849:
843:
842:
840:
839:
834:
829:
828:
827:
817:
811:
810:
809:
804:
799:
794:
789:
784:
774:
773:
772:
767:
760:Multiprocessor
757:
752:
747:
742:
737:
736:
735:
730:
725:
724:
723:
718:
713:
702:
691:
689:
683:
682:
680:
679:
674:
673:
672:
667:
662:
652:
647:
641:
639:
633:
632:
630:
629:
624:
619:
614:
609:
604:
599:
593:
591:
587:
586:
584:
583:
578:
573:
568:
563:
557:
555:
551:
550:
548:
547:
542:
537:
532:
527:
522:
517:
512:
507:
501:
499:
495:
494:
492:
491:
489:Hardware scout
486:
480:
475:
470:
464:
459:
453:
447:
445:
443:Multithreading
439:
438:
436:
435:
430:
425:
420:
415:
410:
405:
400:
394:
392:
388:
387:
385:
384:
382:Systolic array
379:
374:
369:
364:
359:
354:
349:
344:
339:
333:
331:
327:
326:
321:
319:
318:
311:
304:
296:
290:
289:
284:
277:
276:External links
274:
271:
270:
252:
240:
237:on 2021-01-05.
202:
201:
199:
196:
195:
194:
189:
182:
179:
167:
166:
165:
164:
158:
151:
114:
111:
71:
70:Basic concepts
68:
33:
29:Memory barrier
24:
14:
13:
10:
9:
6:
4:
3:
2:
1088:
1077:
1074:
1072:
1069:
1068:
1066:
1051:
1042:
1041:
1038:
1032:
1029:
1027:
1024:
1022:
1019:
1017:
1014:
1012:
1009:
1007:
1004:
1002:
999:
997:
994:
992:
989:
988:
986:
982:
976:
973:
971:
968:
966:
963:
961:
958:
956:
953:
951:
948:
946:
943:
941:
938:
936:
933:
931:
928:
926:
923:
921:
918:
916:
913:
911:
908:
906:
905:Global Arrays
903:
901:
898:
896:
893:
891:
888:
886:
883:
881:
878:
876:
873:
871:
868:
866:
863:
861:
858:
856:
853:
852:
850:
848:
844:
838:
835:
833:
832:Grid computer
830:
826:
823:
822:
821:
818:
815:
812:
808:
805:
803:
800:
798:
795:
793:
790:
788:
785:
783:
780:
779:
778:
775:
771:
768:
766:
763:
762:
761:
758:
756:
753:
751:
748:
746:
743:
741:
738:
734:
731:
729:
726:
722:
719:
717:
714:
711:
708:
707:
706:
703:
701:
698:
697:
696:
693:
692:
690:
688:
684:
678:
675:
671:
668:
666:
663:
661:
658:
657:
656:
653:
651:
648:
646:
643:
642:
640:
638:
634:
628:
625:
623:
620:
618:
615:
613:
610:
608:
605:
603:
600:
598:
595:
594:
592:
588:
582:
579:
577:
574:
572:
569:
567:
564:
562:
559:
558:
556:
552:
546:
543:
541:
538:
536:
533:
531:
528:
526:
523:
521:
518:
516:
513:
511:
508:
506:
503:
502:
500:
496:
490:
487:
484:
481:
479:
476:
474:
471:
468:
465:
463:
460:
457:
454:
452:
449:
448:
446:
444:
440:
434:
431:
429:
426:
424:
421:
419:
416:
414:
411:
409:
406:
404:
401:
399:
396:
395:
393:
389:
383:
380:
378:
375:
373:
370:
368:
365:
363:
360:
358:
355:
353:
350:
348:
345:
343:
340:
338:
335:
334:
332:
328:
324:
317:
312:
310:
305:
303:
298:
297:
294:
288:
285:
283:
280:
279:
275:
266:
262:
256:
253:
249:
244:
241:
233:
229:
222:
216:
214:
212:
210:
208:
204:
197:
193:
190:
188:
185:
184:
180:
178:
175:
174:failed node.
171:
162:
159:
156:
155:fibre channel
152:
149:
145:
142:
141:
140:
139:
138:
136:
131:
128:
127:power fencing
124:
119:
112:
110:
108:
104:
100:
95:
93:
89:
85:
80:
78:
69:
67:
63:
61:
57:
53:
47:
44:
39:
30:
19:
590:Coordination
520:Amdahl's law
456:Simultaneous
264:
255:
247:
243:
232:the original
227:
176:
172:
168:
143:
134:
132:
126:
120:
116:
96:
81:
73:
64:
51:
50:
18:Node fencing
1026:Scalability
787:distributed
670:Concurrency
637:Programming
478:Cooperative
467:Speculative
403:Instruction
1065:Categories
1031:Starvation
770:asymmetric
505:PRAM model
473:Preemptive
198:References
765:symmetric
510:PEM model
146:uses the
92:processes
996:Deadlock
984:Problems
950:pthreads
930:OpenHMPP
855:Ateji PX
816:computer
687:Hardware
554:Elements
540:Slowdown
451:Temporal
433:Pipeline
192:Failover
181:See also
955:RaftLib
935:OpenACC
910:GPUOpen
900:C++ AMP
875:Charm++
617:Barrier
561:Process
545:Speedup
330:General
123:STONITH
77:STONITH
52:Fencing
1048:
925:OpenCL
920:OpenMP
865:Chapel
782:shared
777:Memory
712:(SIMT)
655:Models
566:Thread
498:Theory
469:(SpMT)
423:Memory
408:Thread
391:Levels
895:Dryad
860:Boost
581:Array
571:Fiber
485:(CMT)
458:(SMT)
372:GPGPU
235:(PDF)
224:(PDF)
148:SCSI3
58:of a
960:ROCm
890:CUDA
880:Cilk
847:APIs
807:COMA
802:NUMA
733:MIMD
728:MISD
705:SIMD
700:SISD
428:Loop
418:Data
413:Task
157:port
133:The
121:The
99:hang
56:node
975:ZPL
970:TBB
965:UPC
945:PVM
915:MPI
870:HPX
797:UMA
398:Bit
84:I/O
43:NEC
41:An
1067::
263:.
226:.
206:^
315:e
308:t
301:v
267:.
31:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
