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Based on kernel version 3.9. Page generated on 2013-05-02 23:07 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	  discard
43		Issue command to let the block device reclaim space freed by the
44		filesystem.  This is useful for SSD devices, thinly provisioned
45		LUNs and virtual machine images, but may have a performance
46		impact.
47	
48	  dmapi
49		Enable the DMAPI (Data Management API) event callouts.
50		Use with the "mtpt" option.
51	
52	  grpid/bsdgroups and nogrpid/sysvgroups
53		These options define what group ID a newly created file gets.
54		When grpid is set, it takes the group ID of the directory in
55		which it is created; otherwise (the default) it takes the fsgid
56		of the current process, unless the directory has the setgid bit
57		set, in which case it takes the gid from the parent directory,
58		and also gets the setgid bit set if it is a directory itself.
59	
60	  ihashsize=value
61		In memory inode hashes have been removed, so this option has
62		no function as of August 2007. Option is deprecated.
63	
64	  ikeep/noikeep
65		When ikeep is specified, XFS does not delete empty inode clusters
66		and keeps them around on disk. ikeep is the traditional XFS
67		behaviour. When noikeep is specified, empty inode clusters
68		are returned to the free space pool. The default is noikeep for
69		non-DMAPI mounts, while ikeep is the default when DMAPI is in use.
70	
71	  inode64
72		Indicates that XFS is allowed to create inodes at any location
73		in the filesystem, including those which will result in inode
74		numbers occupying more than 32 bits of significance.  This is
75		the default allocation option. Applications which do not handle
76		inode numbers bigger than 32 bits, should use inode32 option.
77	
78	  inode32
79		Indicates that XFS is limited to create inodes at locations which
80		will not result in inode numbers with more than 32 bits of
81		significance. This is provided for backwards compatibility, since
82		64 bits inode numbers might cause problems for some applications
83		that cannot handle large inode numbers.
84	
85	  largeio/nolargeio
86		If "nolargeio" is specified, the optimal I/O reported in
87		st_blksize by stat(2) will be as small as possible to allow user
88		applications to avoid inefficient read/modify/write I/O.
89		If "largeio" specified, a filesystem that has a "swidth" specified
90		will return the "swidth" value (in bytes) in st_blksize. If the
91		filesystem does not have a "swidth" specified but does specify
92		an "allocsize" then "allocsize" (in bytes) will be returned
93		instead.
94		If neither of these two options are specified, then filesystem
95		will behave as if "nolargeio" was specified.
96	
97	  logbufs=value
98		Set the number of in-memory log buffers.  Valid numbers range
99		from 2-8 inclusive.
100		The default value is 8 buffers for filesystems with a
101		blocksize of 64KiB, 4 buffers for filesystems with a blocksize
102		of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB
103		and 2 buffers for all other configurations.  Increasing the
104		number of buffers may increase performance on some workloads
105		at the cost of the memory used for the additional log buffers
106		and their associated control structures.
107	
108	  logbsize=value
109		Set the size of each in-memory log buffer.
110		Size may be specified in bytes, or in kilobytes with a "k" suffix.
111		Valid sizes for version 1 and version 2 logs are 16384 (16k) and
112		32768 (32k).  Valid sizes for version 2 logs also include
113		65536 (64k), 131072 (128k) and 262144 (256k).
114		The default value for machines with more than 32MiB of memory
115		is 32768, machines with less memory use 16384 by default.
116	
117	  logdev=device and rtdev=device
118		Use an external log (metadata journal) and/or real-time device.
119		An XFS filesystem has up to three parts: a data section, a log
120		section, and a real-time section.  The real-time section is
121		optional, and the log section can be separate from the data
122		section or contained within it.
123	
124	  mtpt=mountpoint
125		Use with the "dmapi" option.  The value specified here will be
126		included in the DMAPI mount event, and should be the path of
127		the actual mountpoint that is used.
128	
129	  noalign
130		Data allocations will not be aligned at stripe unit boundaries.
131	
132	  noatime
133		Access timestamps are not updated when a file is read.
134	
135	  norecovery
136		The filesystem will be mounted without running log recovery.
137		If the filesystem was not cleanly unmounted, it is likely to
138		be inconsistent when mounted in "norecovery" mode.
139		Some files or directories may not be accessible because of this.
140		Filesystems mounted "norecovery" must be mounted read-only or
141		the mount will fail.
142	
143	  nouuid
144		Don't check for double mounted file systems using the file system uuid.
145		This is useful to mount LVM snapshot volumes.
146	
147	  uquota/usrquota/uqnoenforce/quota
148		User disk quota accounting enabled, and limits (optionally)
149		enforced.  Refer to xfs_quota(8) for further details.
150	
151	  gquota/grpquota/gqnoenforce
152		Group disk quota accounting enabled and limits (optionally)
153		enforced.  Refer to xfs_quota(8) for further details.
154	
155	  pquota/prjquota/pqnoenforce
156		Project disk quota accounting enabled and limits (optionally)
157		enforced.  Refer to xfs_quota(8) for further details.
158	
159	  sunit=value and swidth=value
160		Used to specify the stripe unit and width for a RAID device or
161		a stripe volume.  "value" must be specified in 512-byte block
162		units.
163		If this option is not specified and the filesystem was made on
164		a stripe volume or the stripe width or unit were specified for
165		the RAID device at mkfs time, then the mount system call will
166		restore the value from the superblock.  For filesystems that
167		are made directly on RAID devices, these options can be used
168		to override the information in the superblock if the underlying
169		disk layout changes after the filesystem has been created.
170		The "swidth" option is required if the "sunit" option has been
171		specified, and must be a multiple of the "sunit" value.
172	
173	  swalloc
174		Data allocations will be rounded up to stripe width boundaries
175		when the current end of file is being extended and the file
176		size is larger than the stripe width size.
177	
178	
179	sysctls
180	=======
181	
182	The following sysctls are available for the XFS filesystem:
183	
184	  fs.xfs.stats_clear		(Min: 0  Default: 0  Max: 1)
185		Setting this to "1" clears accumulated XFS statistics
186		in /proc/fs/xfs/stat.  It then immediately resets to "0".
187	
188	  fs.xfs.xfssyncd_centisecs	(Min: 100  Default: 3000  Max: 720000)
189	  	The interval at which the xfssyncd thread flushes metadata
190	  	out to disk.  This thread will flush log activity out, and
191	  	do some processing on unlinked inodes.
192	
193	  fs.xfs.xfsbufd_centisecs	(Min: 50  Default: 100	Max: 3000)
194		The interval at which xfsbufd scans the dirty metadata buffers list.
195	
196	  fs.xfs.age_buffer_centisecs	(Min: 100  Default: 1500  Max: 720000)
197		The age at which xfsbufd flushes dirty metadata buffers to disk.
198	
199	  fs.xfs.error_level		(Min: 0  Default: 3  Max: 11)
200		A volume knob for error reporting when internal errors occur.
201		This will generate detailed messages & backtraces for filesystem
202		shutdowns, for example.  Current threshold values are:
203	
204			XFS_ERRLEVEL_OFF:       0
205			XFS_ERRLEVEL_LOW:       1
206			XFS_ERRLEVEL_HIGH:      5
207	
208	  fs.xfs.panic_mask		(Min: 0  Default: 0  Max: 127)
209		Causes certain error conditions to call BUG(). Value is a bitmask;
210		AND together the tags which represent errors which should cause panics:
211	
212			XFS_NO_PTAG                     0
213			XFS_PTAG_IFLUSH                 0x00000001
214			XFS_PTAG_LOGRES                 0x00000002
215			XFS_PTAG_AILDELETE              0x00000004
216			XFS_PTAG_ERROR_REPORT           0x00000008
217			XFS_PTAG_SHUTDOWN_CORRUPT       0x00000010
218			XFS_PTAG_SHUTDOWN_IOERROR       0x00000020
219			XFS_PTAG_SHUTDOWN_LOGERROR      0x00000040
220	
221		This option is intended for debugging only.
222	
223	  fs.xfs.irix_symlink_mode	(Min: 0  Default: 0  Max: 1)
224		Controls whether symlinks are created with mode 0777 (default)
225		or whether their mode is affected by the umask (irix mode).
226	
227	  fs.xfs.irix_sgid_inherit	(Min: 0  Default: 0  Max: 1)
228		Controls files created in SGID directories.
229		If the group ID of the new file does not match the effective group
230		ID or one of the supplementary group IDs of the parent dir, the
231		ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
232		is set.
233	
234	  fs.xfs.inherit_sync		(Min: 0  Default: 1  Max: 1)
235		Setting this to "1" will cause the "sync" flag set
236		by the xfs_io(8) chattr command on a directory to be
237		inherited by files in that directory.
238	
239	  fs.xfs.inherit_nodump		(Min: 0  Default: 1  Max: 1)
240		Setting this to "1" will cause the "nodump" flag set
241		by the xfs_io(8) chattr command on a directory to be
242		inherited by files in that directory.
243	
244	  fs.xfs.inherit_noatime	(Min: 0  Default: 1  Max: 1)
245		Setting this to "1" will cause the "noatime" flag set
246		by the xfs_io(8) chattr command on a directory to be
247		inherited by files in that directory.
248	
249	  fs.xfs.inherit_nosymlinks	(Min: 0  Default: 1  Max: 1)
250		Setting this to "1" will cause the "nosymlinks" flag set
251		by the xfs_io(8) chattr command on a directory to be
252		inherited by files in that directory.
253	
254	  fs.xfs.rotorstep		(Min: 1  Default: 1  Max: 256)
255		In "inode32" allocation mode, this option determines how many
256		files the allocator attempts to allocate in the same allocation
257		group before moving to the next allocation group.  The intent
258		is to control the rate at which the allocator moves between
259		allocation groups when allocating extents for new files.
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