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1
2The SGI XFS Filesystem
3======================
4
5XFS is a high performance journaling filesystem which originated
6on the SGI IRIX platform. It is completely multi-threaded, can
7support large files and large filesystems, extended attributes,
8variable block sizes, is extent based, and makes extensive use of
9Btrees (directories, extents, free space) to aid both performance
10and scalability.
11
12Refer to the documentation at http://oss.sgi.com/projects/xfs/
13for further details. This implementation is on-disk compatible
14with the IRIX version of XFS.
15
16
17Mount Options
18=============
19
20When mounting an XFS filesystem, the following options are accepted.
21
22 biosize=size
23 Sets the preferred buffered I/O size (default size is 64K).
24 "size" must be expressed as the logarithm (base2) of the
25 desired I/O size.
26 Valid values for this option are 14 through 16, inclusive
27 (i.e. 16K, 32K, and 64K bytes). On machines with a 4K
28 pagesize, 13 (8K bytes) is also a valid size.
29 The preferred buffered I/O size can also be altered on an
30 individual file basis using the ioctl(2) system call.
31
32 ikeep/noikeep
33 When inode clusters are emptied of inodes, keep them around
34 on the disk (ikeep) - this is the traditional XFS behaviour
35 and is still the default for now. Using the noikeep option,
36 inode clusters are returned to the free space pool.
37
38 logbufs=value
39 Set the number of in-memory log buffers. Valid numbers range
40 from 2-8 inclusive.
41 The default value is 8 buffers for filesystems with a
42 blocksize of 64K, 4 buffers for filesystems with a blocksize
43 of 32K, 3 buffers for filesystems with a blocksize of 16K
44 and 2 buffers for all other configurations. Increasing the
45 number of buffers may increase performance on some workloads
46 at the cost of the memory used for the additional log buffers
47 and their associated control structures.
48
49 logbsize=value
50 Set the size of each in-memory log buffer.
51 Size may be specified in bytes, or in kilobytes with a "k" suffix.
52 Valid sizes for version 1 and version 2 logs are 16384 (16k) and
53 32768 (32k). Valid sizes for version 2 logs also include
54 65536 (64k), 131072 (128k) and 262144 (256k).
55 The default value for machines with more than 32MB of memory
56 is 32768, machines with less memory use 16384 by default.
57
58 logdev=device and rtdev=device
59 Use an external log (metadata journal) and/or real-time device.
60 An XFS filesystem has up to three parts: a data section, a log
61 section, and a real-time section. The real-time section is
62 optional, and the log section can be separate from the data
63 section or contained within it.
64
65 noalign
66 Data allocations will not be aligned at stripe unit boundaries.
67
68 noatime
69 Access timestamps are not updated when a file is read.
70
71 norecovery
72 The filesystem will be mounted without running log recovery.
73 If the filesystem was not cleanly unmounted, it is likely to
74 be inconsistent when mounted in "norecovery" mode.
75 Some files or directories may not be accessible because of this.
76 Filesystems mounted "norecovery" must be mounted read-only or
77 the mount will fail.
78
79 nouuid
80 Don't check for double mounted file systems using the file system uuid.
81 This is useful to mount LVM snapshot volumes.
82
83 osyncisosync
84 Make O_SYNC writes implement true O_SYNC. WITHOUT this option,
85 Linux XFS behaves as if an "osyncisdsync" option is used,
86 which will make writes to files opened with the O_SYNC flag set
87 behave as if the O_DSYNC flag had been used instead.
88 This can result in better performance without compromising
89 data safety.
90 However if this option is not in effect, timestamp updates from
91 O_SYNC writes can be lost if the system crashes.
92 If timestamp updates are critical, use the osyncisosync option.
93
94 quota/usrquota/uqnoenforce
95 User disk quota accounting enabled, and limits (optionally)
96 enforced.
97
98 grpquota/gqnoenforce
99 Group disk quota accounting enabled and limits (optionally)
100 enforced.
101
102 sunit=value and swidth=value
103 Used to specify the stripe unit and width for a RAID device or
104 a stripe volume. "value" must be specified in 512-byte block
105 units.
106 If this option is not specified and the filesystem was made on
107 a stripe volume or the stripe width or unit were specified for
108 the RAID device at mkfs time, then the mount system call will
109 restore the value from the superblock. For filesystems that
110 are made directly on RAID devices, these options can be used
111 to override the information in the superblock if the underlying
112 disk layout changes after the filesystem has been created.
113 The "swidth" option is required if the "sunit" option has been
114 specified, and must be a multiple of the "sunit" value.
115
116sysctls
117=======
118
119The following sysctls are available for the XFS filesystem:
120
121 fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1)
122 Setting this to "1" clears accumulated XFS statistics
123 in /proc/fs/xfs/stat. It then immediately resets to "0".
124
125 fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000)
126 The interval at which the xfssyncd thread flushes metadata
127 out to disk. This thread will flush log activity out, and
128 do some processing on unlinked inodes.
129
130 fs.xfs.xfsbufd_centisecs (Min: 50 Default: 100 Max: 3000)
131 The interval at which xfsbufd scans the dirty metadata buffers list.
132
133 fs.xfs.age_buffer_centisecs (Min: 100 Default: 1500 Max: 720000)
134 The age at which xfsbufd flushes dirty metadata buffers to disk.
135
136 fs.xfs.error_level (Min: 0 Default: 3 Max: 11)
137 A volume knob for error reporting when internal errors occur.
138 This will generate detailed messages & backtraces for filesystem
139 shutdowns, for example. Current threshold values are:
140
141 XFS_ERRLEVEL_OFF: 0
142 XFS_ERRLEVEL_LOW: 1
143 XFS_ERRLEVEL_HIGH: 5
144
145 fs.xfs.panic_mask (Min: 0 Default: 0 Max: 127)
146 Causes certain error conditions to call BUG(). Value is a bitmask;
147 AND together the tags which represent errors which should cause panics:
148
149 XFS_NO_PTAG 0
150 XFS_PTAG_IFLUSH 0x00000001
151 XFS_PTAG_LOGRES 0x00000002
152 XFS_PTAG_AILDELETE 0x00000004
153 XFS_PTAG_ERROR_REPORT 0x00000008
154 XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010
155 XFS_PTAG_SHUTDOWN_IOERROR 0x00000020
156 XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040
157
158 This option is intended for debugging only.
159
160 fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1)
161 Controls whether symlinks are created with mode 0777 (default)
162 or whether their mode is affected by the umask (irix mode).
163
164 fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1)
165 Controls files created in SGID directories.
166 If the group ID of the new file does not match the effective group
167 ID or one of the supplementary group IDs of the parent dir, the
168 ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
169 is set.
170
171 fs.xfs.restrict_chown (Min: 0 Default: 1 Max: 1)
172 Controls whether unprivileged users can use chown to "give away"
173 a file to another user.
174
175 fs.xfs.inherit_sync (Min: 0 Default: 1 Max 1)
176 Setting this to "1" will cause the "sync" flag set
177 by the chattr(1) command on a directory to be
178 inherited by files in that directory.
179
180 fs.xfs.inherit_nodump (Min: 0 Default: 1 Max 1)
181 Setting this to "1" will cause the "nodump" flag set
182 by the chattr(1) command on a directory to be
183 inherited by files in that directory.
184
185 fs.xfs.inherit_noatime (Min: 0 Default: 1 Max 1)
186 Setting this to "1" will cause the "noatime" flag set
187 by the chattr(1) command on a directory to be
188 inherited by files in that directory.
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