About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / filesystems / xfs.txt




Custom Search

Based on kernel version 2.6.34. Page generated on 2010-05-31 16:02 EST.

1	
2	The SGI XFS Filesystem
3	======================
4	
5	XFS is a high performance journaling filesystem which originated
6	on the SGI IRIX platform.  It is completely multi-threaded, can
7	support large files and large filesystems, extended attributes,
8	variable block sizes, is extent based, and makes extensive use of
9	Btrees (directories, extents, free space) to aid both performance
10	and scalability.
11	
12	Refer to the documentation at http://oss.sgi.com/projects/xfs/
13	for further details.  This implementation is on-disk compatible
14	with the IRIX version of XFS.
15	
16	
17	Mount Options
18	=============
19	
20	When mounting an XFS filesystem, the following options are accepted.
21	
22	  allocsize=size
23		Sets the buffered I/O end-of-file preallocation size when
24		doing delayed allocation writeout (default size is 64KiB).
25		Valid values for this option are page size (typically 4KiB)
26		through to 1GiB, inclusive, in power-of-2 increments.
27	
28	  attr2/noattr2
29		The options enable/disable (default is disabled for backward
30		compatibility on-disk) an "opportunistic" improvement to be
31		made in the way inline extended attributes are stored on-disk.
32		When the new form is used for the first time (by setting or
33		removing extended attributes) the on-disk superblock feature
34		bit field will be updated to reflect this format being in use.
35	
36	  barrier
37		Enables the use of block layer write barriers for writes into
38		the journal and unwritten extent conversion.  This allows for
39		drive level write caching to be enabled, for devices that
40		support write barriers.
41	
42	  dmapi
43		Enable the DMAPI (Data Management API) event callouts.
44		Use with the "mtpt" option.
45	
46	  grpid/bsdgroups and nogrpid/sysvgroups
47		These options define what group ID a newly created file gets.
48		When grpid is set, it takes the group ID of the directory in
49		which it is created; otherwise (the default) it takes the fsgid
50		of the current process, unless the directory has the setgid bit
51		set, in which case it takes the gid from the parent directory,
52		and also gets the setgid bit set if it is a directory itself.
53	
54	  ihashsize=value
55		In memory inode hashes have been removed, so this option has
56		no function as of August 2007. Option is deprecated.
57	
58	  ikeep/noikeep
59		When ikeep is specified, XFS does not delete empty inode clusters
60		and keeps them around on disk. ikeep is the traditional XFS
61		behaviour. When noikeep is specified, empty inode clusters
62		are returned to the free space pool. The default is noikeep for
63		non-DMAPI mounts, while ikeep is the default when DMAPI is in use.
64	
65	  inode64
66		Indicates that XFS is allowed to create inodes at any location
67		in the filesystem, including those which will result in inode
68		numbers occupying more than 32 bits of significance.  This is
69		provided for backwards compatibility, but causes problems for
70		backup applications that cannot handle large inode numbers.
71	
72	  largeio/nolargeio
73		If "nolargeio" is specified, the optimal I/O reported in
74		st_blksize by stat(2) will be as small as possible to allow user
75		applications to avoid inefficient read/modify/write I/O.
76		If "largeio" specified, a filesystem that has a "swidth" specified
77		will return the "swidth" value (in bytes) in st_blksize. If the
78		filesystem does not have a "swidth" specified but does specify
79		an "allocsize" then "allocsize" (in bytes) will be returned
80		instead.
81		If neither of these two options are specified, then filesystem
82		will behave as if "nolargeio" was specified.
83	
84	  logbufs=value
85		Set the number of in-memory log buffers.  Valid numbers range
86		from 2-8 inclusive.
87		The default value is 8 buffers for filesystems with a
88		blocksize of 64KiB, 4 buffers for filesystems with a blocksize
89		of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB
90		and 2 buffers for all other configurations.  Increasing the
91		number of buffers may increase performance on some workloads
92		at the cost of the memory used for the additional log buffers
93		and their associated control structures.
94	
95	  logbsize=value
96		Set the size of each in-memory log buffer.
97		Size may be specified in bytes, or in kilobytes with a "k" suffix.
98		Valid sizes for version 1 and version 2 logs are 16384 (16k) and
99		32768 (32k).  Valid sizes for version 2 logs also include
100		65536 (64k), 131072 (128k) and 262144 (256k).
101		The default value for machines with more than 32MiB of memory
102		is 32768, machines with less memory use 16384 by default.
103	
104	  logdev=device and rtdev=device
105		Use an external log (metadata journal) and/or real-time device.
106		An XFS filesystem has up to three parts: a data section, a log
107		section, and a real-time section.  The real-time section is
108		optional, and the log section can be separate from the data
109		section or contained within it.
110	
111	  mtpt=mountpoint
112		Use with the "dmapi" option.  The value specified here will be
113		included in the DMAPI mount event, and should be the path of
114		the actual mountpoint that is used.
115	
116	  noalign
117		Data allocations will not be aligned at stripe unit boundaries.
118	
119	  noatime
120		Access timestamps are not updated when a file is read.
121	
122	  norecovery
123		The filesystem will be mounted without running log recovery.
124		If the filesystem was not cleanly unmounted, it is likely to
125		be inconsistent when mounted in "norecovery" mode.
126		Some files or directories may not be accessible because of this.
127		Filesystems mounted "norecovery" must be mounted read-only or
128		the mount will fail.
129	
130	  nouuid
131		Don't check for double mounted file systems using the file system uuid.
132		This is useful to mount LVM snapshot volumes.
133	
134	  osyncisosync
135		Make O_SYNC writes implement true O_SYNC.  WITHOUT this option,
136		Linux XFS behaves as if an "osyncisdsync" option is used,
137		which will make writes to files opened with the O_SYNC flag set
138		behave as if the O_DSYNC flag had been used instead.
139		This can result in better performance without compromising
140		data safety.
141		However if this option is not in effect, timestamp updates from
142		O_SYNC writes can be lost if the system crashes.
143		If timestamp updates are critical, use the osyncisosync option.
144	
145	  uquota/usrquota/uqnoenforce/quota
146		User disk quota accounting enabled, and limits (optionally)
147		enforced.  Refer to xfs_quota(8) for further details.
148	
149	  gquota/grpquota/gqnoenforce
150		Group disk quota accounting enabled and limits (optionally)
151		enforced.  Refer to xfs_quota(8) for further details.
152	
153	  pquota/prjquota/pqnoenforce
154		Project disk quota accounting enabled and limits (optionally)
155		enforced.  Refer to xfs_quota(8) for further details.
156	
157	  sunit=value and swidth=value
158		Used to specify the stripe unit and width for a RAID device or
159		a stripe volume.  "value" must be specified in 512-byte block
160		units.
161		If this option is not specified and the filesystem was made on
162		a stripe volume or the stripe width or unit were specified for
163		the RAID device at mkfs time, then the mount system call will
164		restore the value from the superblock.  For filesystems that
165		are made directly on RAID devices, these options can be used
166		to override the information in the superblock if the underlying
167		disk layout changes after the filesystem has been created.
168		The "swidth" option is required if the "sunit" option has been
169		specified, and must be a multiple of the "sunit" value.
170	
171	  swalloc
172		Data allocations will be rounded up to stripe width boundaries
173		when the current end of file is being extended and the file
174		size is larger than the stripe width size.
175	
176	
177	sysctls
178	=======
179	
180	The following sysctls are available for the XFS filesystem:
181	
182	  fs.xfs.stats_clear		(Min: 0  Default: 0  Max: 1)
183		Setting this to "1" clears accumulated XFS statistics
184		in /proc/fs/xfs/stat.  It then immediately resets to "0".
185	
186	  fs.xfs.xfssyncd_centisecs	(Min: 100  Default: 3000  Max: 720000)
187	  	The interval at which the xfssyncd thread flushes metadata
188	  	out to disk.  This thread will flush log activity out, and
189	  	do some processing on unlinked inodes.
190	
191	  fs.xfs.xfsbufd_centisecs	(Min: 50  Default: 100	Max: 3000)
192		The interval at which xfsbufd scans the dirty metadata buffers list.
193	
194	  fs.xfs.age_buffer_centisecs	(Min: 100  Default: 1500  Max: 720000)
195		The age at which xfsbufd flushes dirty metadata buffers to disk.
196	
197	  fs.xfs.error_level		(Min: 0  Default: 3  Max: 11)
198		A volume knob for error reporting when internal errors occur.
199		This will generate detailed messages & backtraces for filesystem
200		shutdowns, for example.  Current threshold values are:
201	
202			XFS_ERRLEVEL_OFF:       0
203			XFS_ERRLEVEL_LOW:       1
204			XFS_ERRLEVEL_HIGH:      5
205	
206	  fs.xfs.panic_mask		(Min: 0  Default: 0  Max: 127)
207		Causes certain error conditions to call BUG(). Value is a bitmask;
208		AND together the tags which represent errors which should cause panics:
209	
210			XFS_NO_PTAG                     0
211			XFS_PTAG_IFLUSH                 0x00000001
212			XFS_PTAG_LOGRES                 0x00000002
213			XFS_PTAG_AILDELETE              0x00000004
214			XFS_PTAG_ERROR_REPORT           0x00000008
215			XFS_PTAG_SHUTDOWN_CORRUPT       0x00000010
216			XFS_PTAG_SHUTDOWN_IOERROR       0x00000020
217			XFS_PTAG_SHUTDOWN_LOGERROR      0x00000040
218	
219		This option is intended for debugging only.
220	
221	  fs.xfs.irix_symlink_mode	(Min: 0  Default: 0  Max: 1)
222		Controls whether symlinks are created with mode 0777 (default)
223		or whether their mode is affected by the umask (irix mode).
224	
225	  fs.xfs.irix_sgid_inherit	(Min: 0  Default: 0  Max: 1)
226		Controls files created in SGID directories.
227		If the group ID of the new file does not match the effective group
228		ID or one of the supplementary group IDs of the parent dir, the
229		ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
230		is set.
231	
232	  fs.xfs.inherit_sync		(Min: 0  Default: 1  Max: 1)
233		Setting this to "1" will cause the "sync" flag set
234		by the xfs_io(8) chattr command on a directory to be
235		inherited by files in that directory.
236	
237	  fs.xfs.inherit_nodump		(Min: 0  Default: 1  Max: 1)
238		Setting this to "1" will cause the "nodump" flag set
239		by the xfs_io(8) chattr command on a directory to be
240		inherited by files in that directory.
241	
242	  fs.xfs.inherit_noatime	(Min: 0  Default: 1  Max: 1)
243		Setting this to "1" will cause the "noatime" flag set
244		by the xfs_io(8) chattr command on a directory to be
245		inherited by files in that directory.
246	
247	  fs.xfs.inherit_nosymlinks	(Min: 0  Default: 1  Max: 1)
248		Setting this to "1" will cause the "nosymlinks" flag set
249		by the xfs_io(8) chattr command on a directory to be
250		inherited by files in that directory.
251	
252	  fs.xfs.rotorstep		(Min: 1  Default: 1  Max: 256)
253		In "inode32" allocation mode, this option determines how many
254		files the allocator attempts to allocate in the same allocation
255		group before moving to the next allocation group.  The intent
256		is to control the rate at which the allocator moves between
257		allocation groups when allocating extents for new files.
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog
Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.