83:. Each summary block contains a pointer to the next summary block, linking segments into one long chain that LFS treats as a linear log. The segments do not necessarily have to be adjacent to each other on disk; for this reason, larger segment sizes (between 384KB and 1MB) are recommended because they amortize the cost of seeking between segments.
132:
Generally, garbage collection is delayed until there are no clean segments left; it can also be deferred for when the system is idle. Even then, only the least-dirty segments are picked for collection. This is intended to avoid the penalty of cleaning full segments when I/O bandwidth is most
71:
and directory formats are almost identical. This allows well-tested UFS file system code to be re-used; current implementations of LFS share the higher-level UFS code with the lower-level code for FFS, since both of these file systems share much in common with UFS.
103:
Unlike UFS, inodes in LFS do not have fixed locations. An inode map—a flat list of inode block locations—is used to track them. As with everything else, inode map blocks are also written to the log when they are changed.
207:
Matthews, Jeanna Neefe; Roselli, Drew; Costello, Adam M.; Wang, Randolph Y.; Anderson, Thomas E. (October 1997), "Improving the performance of log-structured file systems with adaptive methods",
129:
ones by copying live blocks from the dirty segment into the current segment and skipping the rest. The summary block in each segment contains a map to track live blocks.
172:
LFS becomes progressively less efficient as it nears maximum capacity, when the garbage collector has to run almost constantly to make clean segments available.
140:(usually scheduled about once every 30 seconds), LFS writes the last known block locations of the inode map and the number of the current segment to a
165:
in LFS, especially for slowly growing files or multiple simultaneous large writes. This inflicts a severe performance penalty, even though the
390:
365:
121:
1622:
1097:
1612:
783:
592:
226:
1234:
900:
582:
152:
work the same way—the file system simply reconstructs its state from the last checkpoint and resumes logging from there.
40:
55:
implementation was nonfunctional until work leading up to the 4.0 release made it viable again as a production file system.
679:
1617:
1033:
607:
1538:
1386:
1318:
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419:
176:
144:
at a fixed place on disk. There are two such regions; LFS alternates between them each checkpoint. Once written, a
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32:
17:
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669:
179:
or versioning, even though both features are trivial to implement in general on log-structured file systems.
1433:
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351:
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1102:
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148:
represents the last consistent snapshot of the file system. Recovery after a crash and normal
1453:
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222:
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64:
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397:
36:
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586:
457:
190:
Seltzer, Margo; Bostic, Keith; McKusick, Marshall Kirk; Staelin, Carl (January 1993),
119:
blocks, or blocks for which no newer copies exist further ahead in the log. The LFS
1663:
1513:
1458:
1132:
1072:
931:
209:
Proceedings of the sixteenth ACM symposium on
Operating systems principles - SOSP '97
191:
325:
310:
236:
1577:
1285:
873:
840:
778:
758:
79:, only one of which is active at any one time. Each segment has a header called a
283:
1275:
374:
1553:
1351:
169:
for log-structured file systems assumes disk reads will mostly be cached away.
86:
Whenever a file or directory is changed, LFS writes to the head of this log:
1508:
1249:
1127:
858:
726:
721:
16:
This article is about the NetBSD file system. For the general concept, see
302:
217:
1326:
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602:
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449:
1280:
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531:
48:
44:
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52:
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68:
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819:
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521:
486:
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347:
343:
107:
When a segment is filled, LFS goes on to fill the next free or
825:
805:
694:
596:
284:"The Design and Implementation of a Log-Structured Filesystem"
192:"An Implementation of a Log-Structured File System for UNIX"
282:
Rosenblum, Mendel; Ousterhout, John K (February 1992),
1631:
1603:
1568:
1524:
1442:
1364:
1317:
1263:
1158:
1063:
989:
929:
872:
839:
406:
324:Rosenblum, Mendel; Ousterhout, John K (June 1990),
63:Most of the on-disk format of LFS is borrowed from
35:(a concept originally proposed and implemented by
277:
275:
359:
8:
1446:
1162:
926:
412:
366:
352:
344:
216:
99:Inode map blocks updated to point at (3).
93:Indirect blocks updated to point to (1).
249:
333:Proceedings of the 1990 Summer Usenix
199:Proceedings of the 1993 Winter Usenix
7:
291:ACM Transactions on Computer Systems
111:segment. Segments are said to be
14:
96:Inodes updated to point to (2).
90:Any changed or new data blocks.
259:"NetBSD 4.0 Release CHANGELOG"
1:
257:Bouyer, Manuel (2007-12-15).
39:), originally developed for
31:) is an implementation of a
1539:Filesystem-level encryption
1686:
386:Comparison of file systems
125:turns dirty segments into
75:LFS divides the disk into
33:log-structured file system
25:Log-Structured File System
18:log-structured file system
15:
1449:
1165:
415:
381:
326:"The LFS Storage Manager"
163:file system fragmentation
1489:Extended file attributes
1190:Compact Disc File System
1588:Installable File System
67:. The indirect block,
43:. It was removed from
636:TiVo Media File System
500:Encrypting File System
631:Macintosh File System
303:10.1145/146941.146943
218:10.1145/268998.266700
1644:GUID Partition Table
991:Distributed parallel
739:Shared File System (
211:, pp. 238–251,
161:There can be severe
1649:Apple Partition Map
1595:Virtual file system
1534:Access-control list
648:NetWare File System
175:LFS does not allow
1639:Master Boot Record
1464:Data deduplication
1103:Google File System
1019:Google File System
505:Extent File System
467:Byte File System (
1670:Disk file systems
1657:
1656:
1564:
1563:
1454:Case preservation
1360:
1359:
1059:
1058:
985:
984:
747:Smart File System
142:checkpoint region
122:garbage collector
1677:
1474:Execute in place
1447:
1180:Boot File System
1163:
927:
463:Boot File System
413:
368:
361:
354:
345:
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321:
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288:
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268:
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239:
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196:
167:design rationale
115:if they contain
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1660:
1659:
1658:
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1627:
1599:
1583:File system API
1560:
1520:
1496:File change log
1438:
1414:Record-oriented
1387:Self-certifying
1356:
1313:
1259:
1154:
1055:
981:
925:
868:
835:
408:
402:
398:Unix filesystem
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61:
37:John Ousterhout
21:
12:
11:
5:
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1623:Log-structured
1620:
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1551:
1541:
1536:
1530:
1528:
1526:Access control
1522:
1521:
1519:
1518:
1517:
1516:
1511:
1503:
1498:
1493:
1492:
1491:
1484:File attribute
1481:
1476:
1471:
1469:Data scrubbing
1466:
1461:
1456:
1450:
1444:
1440:
1439:
1437:
1436:
1431:
1426:
1424:Steganographic
1421:
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1404:Log-structured
1401:
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787:
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781:
771:
766:
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756:
751:
750:
749:
744:
734:
729:
727:Reliance Nitro
724:
719:
718:
717:
707:
702:
697:
692:
687:
682:
677:
672:
667:
666:
665:
655:
650:
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638:
633:
625:
620:
615:
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605:
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590:
587:Classic Mac OS
580:
579:
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563:
558:
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541:
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524:
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494:
489:
484:
479:
474:
473:
472:
465:
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458:Be File System
452:
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228:978-0897919166
227:
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157:
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101:
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97:
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13:
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3:
2:
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1614:
1613:Cryptographic
1611:
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1596:
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1465:
1462:
1460:
1459:Copy-on-write
1457:
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1119:
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1111:
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1101:
1099:
1096:
1094:
1091:
1089:
1086:
1083:
1079:
1076:
1074:
1071:
1070:
1068:
1066:
1062:
1052:
1051:
1047:
1045:
1042:
1040:
1037:
1035:
1032:
1030:
1027:
1025:
1022:
1020:
1017:
1015:
1012:
1010:
1007:
1005:
1002:
1000:
997:
996:
994:
992:
988:
978:
975:
973:
970:
966:
963:
962:
961:
958:
956:
953:
951:
948:
946:
943:
941:
938:
937:
935:
933:
932:wear leveling
928:
922:
919:
917:
914:
912:
909:
907:
904:
902:
899:
897:
894:
892:
889:
887:
884:
883:
881:
879:
875:
871:
865:
862:
860:
857:
855:
852:
850:
847:
846:
844:
842:
838:
831:
827:
824:
821:
817:
814:
812:
809:
807:
804:
802:
799:
797:
794:
792:
789:
785:
782:
780:
777:
776:
775:
772:
770:
767:
765:
762:
760:
757:
755:
752:
748:
745:
742:
738:
737:
735:
733:
730:
728:
725:
723:
720:
716:
713:
712:
711:
708:
706:
703:
701:
698:
696:
693:
691:
688:
686:
683:
681:
678:
676:
673:
671:
668:
664:
661:
660:
659:
656:
654:
651:
649:
646:
644:
641:
637:
634:
632:
629:
628:
626:
624:
621:
619:
616:
614:
611:
609:
606:
604:
601:
598:
594:
591:
588:
584:
581:
577:
574:
573:
572:
569:
567:
564:
562:
559:
557:
554:
550:
547:
546:
545:
542:
538:
535:
533:
530:
528:
525:
523:
520:
519:
518:
515:
513:
510:
506:
503:
501:
498:
497:
495:
493:
490:
488:
485:
483:
480:
478:
475:
470:
466:
464:
461:
459:
456:
455:
453:
451:
448:
446:
443:
441:
438:
436:
433:
431:
428:
426:
423:
421:
418:
417:
414:
411:
405:
399:
396:
392:
389:
388:
387:
384:
383:
380:
376:
369:
364:
362:
357:
355:
350:
349:
346:
334:
327:
320:
317:
312:
308:
304:
300:
296:
292:
285:
278:
276:
272:
260:
253:
250:
243:
238:
234:
230:
224:
219:
214:
210:
205:
204:
200:
193:
188:
187:
183:
178:
174:
171:
168:
164:
160:
159:
156:Disadvantages
155:
153:
151:
147:
143:
139:
134:
130:
128:
124:
123:
118:
114:
110:
105:
98:
95:
92:
89:
88:
87:
84:
82:
81:summary block
78:
73:
70:
66:
58:
56:
54:
50:
46:
42:
38:
34:
30:
26:
19:
1578:File manager
1147:
1048:
874:Flash memory
841:Optical disc
779:soft updates
759:Soup (Apple)
622:
409:non-rotating
375:File systems
332:
319:
297:(1): 26–52,
294:
290:
262:. Retrieved
252:
208:
198:
177:snapshotting
145:
141:
137:
135:
131:
126:
120:
116:
112:
108:
106:
102:
85:
80:
76:
74:
62:
28:
24:
22:
1544:Permissions
1159:Specialized
391:distributed
1570:Interfaces
1554:Sticky bit
1434:Versioning
1399:Journaling
1342:Rubberhose
1138:SMB (CIFS)
930:host-side
264:2019-02-04
244:References
146:checkpoint
138:checkpoint
1429:Synthetic
1372:Clustered
1319:Encrypted
1250:OverlayFS
859:ISO 13490
435:Amiga OFS
430:Amiga FFS
335:: 315–324
1664:Category
1514:Symbolic
1443:Features
1419:Semantic
1327:eCryptfs
1271:configfs
1240:SquashFS
1128:POHMELFS
1029:OrangeFS
854:ISO 9660
774:UFS/UFS2
722:Reliance
710:ReiserFS
556:Files-11
450:bcachefs
407:Disk and
311:28452863
237:11858758
150:mounting
133:needed.
77:segments
1632:Layouts
1618:Default
1281:debugfs
1255:UnionFS
1149:more...
1082:OpenAFS
1050:more...
715:Reiser4
685:OpenZFS
576:HAMMER2
532:ext3cow
512:Episode
49:OpenBSD
45:FreeBSD
1505:Links
1479:Extent
1409:Object
1377:Global
1295:specfs
1291:procfs
1286:kernfs
1264:Pseudo
1245:UMSDOS
1200:Davfs2
1195:cramfs
1133:Hadoop
1113:Lustre
999:BeeGFS
965:NILFS2
700:QNX4FS
663:NILFS2
571:HAMMER
561:Fossil
309:
235:
225:
59:Design
53:NetBSD
51:; the
1605:Lists
1549:Modes
1394:Flash
1365:Types
1347:SSHFS
1332:EncFS
1309:WinFS
1304:tmpfs
1299:sysfs
1276:devfs
1210:FTPFS
1205:EROFS
1143:SSHFS
1024:OCFS2
977:UBIFS
972:YAFFS
960:NILFS
955:LogFS
950:JFFS2
906:EROFS
896:exFAT
801:Xiafs
784:WAPBL
769:UBIFS
680:OneFS
658:NILFS
653:Next3
643:MINIX
549:exFAT
477:Btrfs
445:AthFS
425:AdvFS
329:(PDF)
307:S2CID
287:(PDF)
233:S2CID
195:(PDF)
184:Notes
136:At a
127:clean
113:dirty
109:clean
69:inode
1509:Hard
1501:Fork
1382:Grid
1235:MVFS
1230:NOVA
1225:LTFS
1220:Lnfs
1215:FUSE
1185:CDfs
1175:AXFS
1170:Aufs
1108:GPFS
1093:Coda
1044:Xsan
1034:PVFS
1014:GFS2
1009:CXFS
1004:Ceph
945:JFFS
940:CHFS
921:NVFS
911:F2FS
901:TFAT
886:APFS
876:and
820:z/OS
811:Xsan
796:WAFL
791:VxFS
764:Tux3
754:SNFS
736:SFS
705:ReFS
675:NTFS
627:MFS
613:HTFS
608:HPFS
603:HFS+
566:GPFS
537:ext4
527:ext3
522:ext2
496:EFS
487:CXFS
482:CVFS
469:z/VM
454:BFS
440:APFS
420:ADFS
223:ISBN
117:live
47:and
27:(or
23:The
1352:ZFS
1337:EFS
1123:NFS
1118:NCP
1098:DFS
1088:AFP
1078:AFS
1065:NAS
1039:QFS
916:JFS
891:FAT
878:SSD
864:UDF
849:HSF
830:Sun
826:ZFS
816:zFS
806:XFS
732:RFS
695:QFS
690:PFS
670:NSS
623:LFS
618:JFS
597:MVS
593:HFS
583:HFS
544:FAT
517:ext
492:DFS
299:doi
213:doi
65:UFS
41:BSD
29:LFS
1666::
1073:9P
741:VM
331:,
305:,
295:10
293:,
289:,
274:^
231:,
221:,
197:,
1084:)
1080:(
832:)
828:(
822:)
818:(
743:)
599:)
595:(
589:)
585:(
471:)
367:e
360:t
353:v
337:.
314:.
301::
269:.
267:.
215::
20:.
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