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Based on kernel version 3.13. Page generated on 2014-01-20 22:03 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	For boolean mount options, the names with the (*) suffix is the
22	default behaviour.
23	
24	  allocsize=size
25		Sets the buffered I/O end-of-file preallocation size when
26		doing delayed allocation writeout (default size is 64KiB).
27		Valid values for this option are page size (typically 4KiB)
28		through to 1GiB, inclusive, in power-of-2 increments.
29	
30		The default behaviour is for dynamic end-of-file
31		preallocation size, which uses a set of heuristics to
32		optimise the preallocation size based on the current
33		allocation patterns within the file and the access patterns
34		to the file. Specifying a fixed allocsize value turns off
35		the dynamic behaviour.
36	
37	  attr2
38	  noattr2
39		The options enable/disable an "opportunistic" improvement to
40		be made in the way inline extended attributes are stored
41		on-disk.  When the new form is used for the first time when
42		attr2 is selected (either when setting or removing extended
43		attributes) the on-disk superblock feature bit field will be
44		updated to reflect this format being in use.
45	
46		The default behaviour is determined by the on-disk feature
47		bit indicating that attr2 behaviour is active. If either
48		mount option it set, then that becomes the new default used
49		by the filesystem.
50	
51		CRC enabled filesystems always use the attr2 format, and so
52		will reject the noattr2 mount option if it is set.
53	
54	  barrier (*)
55	  nobarrier
56		Enables/disables the use of block layer write barriers for
57		writes into the journal and for data integrity operations.
58		This allows for drive level write caching to be enabled, for
59		devices that support write barriers.
60	
61	  discard
62	  nodiscard (*)
63		Enable/disable the issuing of commands to let the block
64		device reclaim space freed by the filesystem.  This is
65		useful for SSD devices, thinly provisioned LUNs and virtual
66		machine images, but may have a performance impact.
67	
68		Note: It is currently recommended that you use the fstrim
69		application to discard unused blocks rather than the discard
70		mount option because the performance impact of this option
71		is quite severe.
72	
73	  grpid/bsdgroups
74	  nogrpid/sysvgroups (*)
75		These options define what group ID a newly created file
76		gets.  When grpid is set, it takes the group ID of the
77		directory in which it is created; otherwise it takes the
78		fsgid of the current process, unless the directory has the
79		setgid bit set, in which case it takes the gid from the
80		parent directory, and also gets the setgid bit set if it is
81		a directory itself.
82	
83	  filestreams
84		Make the data allocator use the filestreams allocation mode
85		across the entire filesystem rather than just on directories
86		configured to use it.
87	
88	  ikeep
89	  noikeep (*)
90		When ikeep is specified, XFS does not delete empty inode
91		clusters and keeps them around on disk.  When noikeep is
92		specified, empty inode clusters are returned to the free
93		space pool.
94	
95	  inode32
96	  inode64 (*)
97		When inode32 is specified, it indicates that XFS limits
98		inode creation to locations which will not result in inode
99		numbers with more than 32 bits of significance.
100	
101		When inode64 is specified, it indicates that XFS is allowed
102		to create inodes at any location in the filesystem,
103		including those which will result in inode numbers occupying
104		more than 32 bits of significance. 
105	
106		inode32 is provided for backwards compatibility with older
107		systems and applications, since 64 bits inode numbers might
108		cause problems for some applications that cannot handle
109		large inode numbers.  If applications are in use which do
110		not handle inode numbers bigger than 32 bits, the inode32
111		option should be specified.
112	
113	
114	  largeio
115	  nolargeio (*)
116		If "nolargeio" is specified, the optimal I/O reported in
117		st_blksize by stat(2) will be as small as possible to allow
118		user applications to avoid inefficient read/modify/write
119		I/O.  This is typically the page size of the machine, as
120		this is the granularity of the page cache.
121	
122		If "largeio" specified, a filesystem that was created with a
123		"swidth" specified will return the "swidth" value (in bytes)
124		in st_blksize. If the filesystem does not have a "swidth"
125		specified but does specify an "allocsize" then "allocsize"
126		(in bytes) will be returned instead. Otherwise the behaviour
127		is the same as if "nolargeio" was specified.
128	
129	  logbufs=value
130		Set the number of in-memory log buffers.  Valid numbers
131		range from 2-8 inclusive.
132	
133		The default value is 8 buffers.
134	
135		If the memory cost of 8 log buffers is too high on small
136		systems, then it may be reduced at some cost to performance
137		on metadata intensive workloads. The logbsize option below
138		controls the size of each buffer and so is also relevant to
139		this case.
140	
141	  logbsize=value
142		Set the size of each in-memory log buffer.  The size may be
143		specified in bytes, or in kilobytes with a "k" suffix.
144		Valid sizes for version 1 and version 2 logs are 16384 (16k)
145		and 32768 (32k).  Valid sizes for version 2 logs also
146		include 65536 (64k), 131072 (128k) and 262144 (256k). The
147		logbsize must be an integer multiple of the log
148		stripe unit configured at mkfs time.
149	
150		The default value for for version 1 logs is 32768, while the
151		default value for version 2 logs is MAX(32768, log_sunit).
152	
153	  logdev=device and rtdev=device
154		Use an external log (metadata journal) and/or real-time device.
155		An XFS filesystem has up to three parts: a data section, a log
156		section, and a real-time section.  The real-time section is
157		optional, and the log section can be separate from the data
158		section or contained within it.
159	
160	  noalign
161		Data allocations will not be aligned at stripe unit
162		boundaries. This is only relevant to filesystems created
163		with non-zero data alignment parameters (sunit, swidth) by
164		mkfs.
165	
166	  norecovery
167		The filesystem will be mounted without running log recovery.
168		If the filesystem was not cleanly unmounted, it is likely to
169		be inconsistent when mounted in "norecovery" mode.
170		Some files or directories may not be accessible because of this.
171		Filesystems mounted "norecovery" must be mounted read-only or
172		the mount will fail.
173	
174	  nouuid
175		Don't check for double mounted file systems using the file
176		system uuid.  This is useful to mount LVM snapshot volumes,
177		and often used in combination with "norecovery" for mounting
178		read-only snapshots.
179	
180	  noquota
181		Forcibly turns off all quota accounting and enforcement
182		within the filesystem.
183	
184	  uquota/usrquota/uqnoenforce/quota
185		User disk quota accounting enabled, and limits (optionally)
186		enforced.  Refer to xfs_quota(8) for further details.
187	
188	  gquota/grpquota/gqnoenforce
189		Group disk quota accounting enabled and limits (optionally)
190		enforced.  Refer to xfs_quota(8) for further details.
191	
192	  pquota/prjquota/pqnoenforce
193		Project disk quota accounting enabled and limits (optionally)
194		enforced.  Refer to xfs_quota(8) for further details.
195	
196	  sunit=value and swidth=value
197		Used to specify the stripe unit and width for a RAID device
198		or a stripe volume.  "value" must be specified in 512-byte
199		block units. These options are only relevant to filesystems
200		that were created with non-zero data alignment parameters.
201	
202		The sunit and swidth parameters specified must be compatible
203		with the existing filesystem alignment characteristics.  In
204		general, that means the only valid changes to sunit are
205		increasing it by a power-of-2 multiple. Valid swidth values
206		are any integer multiple of a valid sunit value.
207	
208		Typically the only time these mount options are necessary if
209		after an underlying RAID device has had it's geometry
210		modified, such as adding a new disk to a RAID5 lun and
211		reshaping it.
212	
213	  swalloc
214		Data allocations will be rounded up to stripe width boundaries
215		when the current end of file is being extended and the file
216		size is larger than the stripe width size.
217	
218	  wsync
219		When specified, all filesystem namespace operations are
220		executed synchronously. This ensures that when the namespace
221		operation (create, unlink, etc) completes, the change to the
222		namespace is on stable storage. This is useful in HA setups
223		where failover must not result in clients seeing
224		inconsistent namespace presentation during or after a
225		failover event.
226	
227	
228	Deprecated Mount Options
229	========================
230	
231	  delaylog/nodelaylog
232		Delayed logging is the only logging method that XFS supports
233		now, so these mount options are now ignored.
234	
235		Due for removal in 3.12.
236	
237	  ihashsize=value
238		In memory inode hashes have been removed, so this option has
239		no function as of August 2007. Option is deprecated.
240	
241		Due for removal in 3.12.
242	
243	  irixsgid
244		This behaviour is now controlled by a sysctl, so the mount
245		option is ignored.
246	
247		Due for removal in 3.12.
248	
249	  osyncisdsync
250	  osyncisosync
251		O_SYNC and O_DSYNC are fully supported, so there is no need
252		for these options any more.
253	
254		Due for removal in 3.12.
255	
256	sysctls
257	=======
258	
259	The following sysctls are available for the XFS filesystem:
260	
261	  fs.xfs.stats_clear		(Min: 0  Default: 0  Max: 1)
262		Setting this to "1" clears accumulated XFS statistics
263		in /proc/fs/xfs/stat.  It then immediately resets to "0".
264	
265	  fs.xfs.xfssyncd_centisecs	(Min: 100  Default: 3000  Max: 720000)
266		The interval at which the filesystem flushes metadata
267		out to disk and runs internal cache cleanup routines.
268	
269	  fs.xfs.filestream_centisecs	(Min: 1  Default: 3000  Max: 360000)
270		The interval at which the filesystem ages filestreams cache
271		references and returns timed-out AGs back to the free stream
272		pool.
273	
274	  fs.xfs.speculative_prealloc_lifetime
275			(Units: seconds   Min: 1  Default: 300  Max: 86400)
276		The interval at which the background scanning for inodes
277		with unused speculative preallocation runs. The scan
278		removes unused preallocation from clean inodes and releases
279		the unused space back to the free pool.
280	
281	  fs.xfs.error_level		(Min: 0  Default: 3  Max: 11)
282		A volume knob for error reporting when internal errors occur.
283		This will generate detailed messages & backtraces for filesystem
284		shutdowns, for example.  Current threshold values are:
285	
286			XFS_ERRLEVEL_OFF:       0
287			XFS_ERRLEVEL_LOW:       1
288			XFS_ERRLEVEL_HIGH:      5
289	
290	  fs.xfs.panic_mask		(Min: 0  Default: 0  Max: 127)
291		Causes certain error conditions to call BUG(). Value is a bitmask;
292		AND together the tags which represent errors which should cause panics:
293	
294			XFS_NO_PTAG                     0
295			XFS_PTAG_IFLUSH                 0x00000001
296			XFS_PTAG_LOGRES                 0x00000002
297			XFS_PTAG_AILDELETE              0x00000004
298			XFS_PTAG_ERROR_REPORT           0x00000008
299			XFS_PTAG_SHUTDOWN_CORRUPT       0x00000010
300			XFS_PTAG_SHUTDOWN_IOERROR       0x00000020
301			XFS_PTAG_SHUTDOWN_LOGERROR      0x00000040
302	
303		This option is intended for debugging only.
304	
305	  fs.xfs.irix_symlink_mode	(Min: 0  Default: 0  Max: 1)
306		Controls whether symlinks are created with mode 0777 (default)
307		or whether their mode is affected by the umask (irix mode).
308	
309	  fs.xfs.irix_sgid_inherit	(Min: 0  Default: 0  Max: 1)
310		Controls files created in SGID directories.
311		If the group ID of the new file does not match the effective group
312		ID or one of the supplementary group IDs of the parent dir, the
313		ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
314		is set.
315	
316	  fs.xfs.inherit_sync		(Min: 0  Default: 1  Max: 1)
317		Setting this to "1" will cause the "sync" flag set
318		by the xfs_io(8) chattr command on a directory to be
319		inherited by files in that directory.
320	
321	  fs.xfs.inherit_nodump		(Min: 0  Default: 1  Max: 1)
322		Setting this to "1" will cause the "nodump" flag set
323		by the xfs_io(8) chattr command on a directory to be
324		inherited by files in that directory.
325	
326	  fs.xfs.inherit_noatime	(Min: 0  Default: 1  Max: 1)
327		Setting this to "1" will cause the "noatime" flag set
328		by the xfs_io(8) chattr command on a directory to be
329		inherited by files in that directory.
330	
331	  fs.xfs.inherit_nosymlinks	(Min: 0  Default: 1  Max: 1)
332		Setting this to "1" will cause the "nosymlinks" flag set
333		by the xfs_io(8) chattr command on a directory to be
334		inherited by files in that directory.
335	
336	  fs.xfs.inherit_nodefrag	(Min: 0  Default: 1  Max: 1)
337		Setting this to "1" will cause the "nodefrag" flag set
338		by the xfs_io(8) chattr command on a directory to be
339		inherited by files in that directory.
340	
341	  fs.xfs.rotorstep		(Min: 1  Default: 1  Max: 256)
342		In "inode32" allocation mode, this option determines how many
343		files the allocator attempts to allocate in the same allocation
344		group before moving to the next allocation group.  The intent
345		is to control the rate at which the allocator moves between
346		allocation groups when allocating extents for new files.
347	
348	Deprecated Sysctls
349	==================
350	
351	  fs.xfs.xfsbufd_centisecs	(Min: 50  Default: 100	Max: 3000)
352		Dirty metadata is now tracked by the log subsystem and
353		flushing is driven by log space and idling demands. The
354		xfsbufd no longer exists, so this syctl does nothing.
355	
356		Due for removal in 3.14.
357	
358	  fs.xfs.age_buffer_centisecs	(Min: 100  Default: 1500  Max: 720000)
359		Dirty metadata is now tracked by the log subsystem and
360		flushing is driven by log space and idling demands. The
361		xfsbufd no longer exists, so this syctl does nothing.
362	
363		Due for removal in 3.14.
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