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. 21For boolean mount options, the names with the (*) suffix is the 22default 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 228Deprecated Mount Options 229======================== 230 231None at present. 232 233 234Removed Mount Options 235===================== 236 237 Name Removed 238 ---- ------- 239 delaylog/nodelaylog v4.0 240 ihashsize v4.0 241 irixsgid v4.0 242 osyncisdsync/osyncisosync v4.0 243 244 245sysctls 246======= 247 248The following sysctls are available for the XFS filesystem: 249 250 fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1) 251 Setting this to "1" clears accumulated XFS statistics 252 in /proc/fs/xfs/stat. It then immediately resets to "0". 253 254 fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000) 255 The interval at which the filesystem flushes metadata 256 out to disk and runs internal cache cleanup routines. 257 258 fs.xfs.filestream_centisecs (Min: 1 Default: 3000 Max: 360000) 259 The interval at which the filesystem ages filestreams cache 260 references and returns timed-out AGs back to the free stream 261 pool. 262 263 fs.xfs.speculative_prealloc_lifetime 264 (Units: seconds Min: 1 Default: 300 Max: 86400) 265 The interval at which the background scanning for inodes 266 with unused speculative preallocation runs. The scan 267 removes unused preallocation from clean inodes and releases 268 the unused space back to the free pool. 269 270 fs.xfs.error_level (Min: 0 Default: 3 Max: 11) 271 A volume knob for error reporting when internal errors occur. 272 This will generate detailed messages & backtraces for filesystem 273 shutdowns, for example. Current threshold values are: 274 275 XFS_ERRLEVEL_OFF: 0 276 XFS_ERRLEVEL_LOW: 1 277 XFS_ERRLEVEL_HIGH: 5 278 279 fs.xfs.panic_mask (Min: 0 Default: 0 Max: 255) 280 Causes certain error conditions to call BUG(). Value is a bitmask; 281 OR together the tags which represent errors which should cause panics: 282 283 XFS_NO_PTAG 0 284 XFS_PTAG_IFLUSH 0x00000001 285 XFS_PTAG_LOGRES 0x00000002 286 XFS_PTAG_AILDELETE 0x00000004 287 XFS_PTAG_ERROR_REPORT 0x00000008 288 XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010 289 XFS_PTAG_SHUTDOWN_IOERROR 0x00000020 290 XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040 291 XFS_PTAG_FSBLOCK_ZERO 0x00000080 292 293 This option is intended for debugging only. 294 295 fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1) 296 Controls whether symlinks are created with mode 0777 (default) 297 or whether their mode is affected by the umask (irix mode). 298 299 fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1) 300 Controls files created in SGID directories. 301 If the group ID of the new file does not match the effective group 302 ID or one of the supplementary group IDs of the parent dir, the 303 ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl 304 is set. 305 306 fs.xfs.inherit_sync (Min: 0 Default: 1 Max: 1) 307 Setting this to "1" will cause the "sync" flag set 308 by the xfs_io(8) chattr command on a directory to be 309 inherited by files in that directory. 310 311 fs.xfs.inherit_nodump (Min: 0 Default: 1 Max: 1) 312 Setting this to "1" will cause the "nodump" flag set 313 by the xfs_io(8) chattr command on a directory to be 314 inherited by files in that directory. 315 316 fs.xfs.inherit_noatime (Min: 0 Default: 1 Max: 1) 317 Setting this to "1" will cause the "noatime" 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_nosymlinks (Min: 0 Default: 1 Max: 1) 322 Setting this to "1" will cause the "nosymlinks" 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_nodefrag (Min: 0 Default: 1 Max: 1) 327 Setting this to "1" will cause the "nodefrag" 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.rotorstep (Min: 1 Default: 1 Max: 256) 332 In "inode32" allocation mode, this option determines how many 333 files the allocator attempts to allocate in the same allocation 334 group before moving to the next allocation group. The intent 335 is to control the rate at which the allocator moves between 336 allocation groups when allocating extents for new files. 337 338Deprecated Sysctls 339================== 340 341None at present. 342 343 344Removed Sysctls 345=============== 346 347 Name Removed 348 ---- ------- 349 fs.xfs.xfsbufd_centisec v4.0 350 fs.xfs.age_buffer_centisecs v4.0 351