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 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 CRC enabled filesystems always use the attr2 format, and so 37 will reject the noattr2 mount option if it is set. 38 39 barrier 40 Enables the use of block layer write barriers for writes into 41 the journal and unwritten extent conversion. This allows for 42 drive level write caching to be enabled, for devices that 43 support write barriers. 44 45 discard 46 Issue command to let the block device reclaim space freed by the 47 filesystem. This is useful for SSD devices, thinly provisioned 48 LUNs and virtual machine images, but may have a performance 49 impact. 50 51 dmapi 52 Enable the DMAPI (Data Management API) event callouts. 53 Use with the "mtpt" option. 54 55 grpid/bsdgroups and nogrpid/sysvgroups 56 These options define what group ID a newly created file gets. 57 When grpid is set, it takes the group ID of the directory in 58 which it is created; otherwise (the default) it takes the fsgid 59 of the current process, unless the directory has the setgid bit 60 set, in which case it takes the gid from the parent directory, 61 and also gets the setgid bit set if it is a directory itself. 62 63 ihashsize=value 64 In memory inode hashes have been removed, so this option has 65 no function as of August 2007. Option is deprecated. 66 67 ikeep/noikeep 68 When ikeep is specified, XFS does not delete empty inode clusters 69 and keeps them around on disk. ikeep is the traditional XFS 70 behaviour. When noikeep is specified, empty inode clusters 71 are returned to the free space pool. The default is noikeep for 72 non-DMAPI mounts, while ikeep is the default when DMAPI is in use. 73 74 inode64 75 Indicates that XFS is allowed to create inodes at any location 76 in the filesystem, including those which will result in inode 77 numbers occupying more than 32 bits of significance. This is 78 the default allocation option. Applications which do not handle 79 inode numbers bigger than 32 bits, should use inode32 option. 80 81 inode32 82 Indicates that XFS is limited to create inodes at locations which 83 will not result in inode numbers with more than 32 bits of 84 significance. This is provided for backwards compatibility, since 85 64 bits inode numbers might cause problems for some applications 86 that cannot handle large inode numbers. 87 88 largeio/nolargeio 89 If "nolargeio" is specified, the optimal I/O reported in 90 st_blksize by stat(2) will be as small as possible to allow user 91 applications to avoid inefficient read/modify/write I/O. 92 If "largeio" specified, a filesystem that has a "swidth" specified 93 will return the "swidth" value (in bytes) in st_blksize. If the 94 filesystem does not have a "swidth" specified but does specify 95 an "allocsize" then "allocsize" (in bytes) will be returned 96 instead. 97 If neither of these two options are specified, then filesystem 98 will behave as if "nolargeio" was specified. 99 100 logbufs=value 101 Set the number of in-memory log buffers. Valid numbers range 102 from 2-8 inclusive. 103 The default value is 8 buffers for filesystems with a 104 blocksize of 64KiB, 4 buffers for filesystems with a blocksize 105 of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB 106 and 2 buffers for all other configurations. Increasing the 107 number of buffers may increase performance on some workloads 108 at the cost of the memory used for the additional log buffers 109 and their associated control structures. 110 111 logbsize=value 112 Set the size of each in-memory log buffer. 113 Size may be specified in bytes, or in kilobytes with a "k" suffix. 114 Valid sizes for version 1 and version 2 logs are 16384 (16k) and 115 32768 (32k). Valid sizes for version 2 logs also include 116 65536 (64k), 131072 (128k) and 262144 (256k). 117 The default value for machines with more than 32MiB of memory 118 is 32768, machines with less memory use 16384 by default. 119 120 logdev=device and rtdev=device 121 Use an external log (metadata journal) and/or real-time device. 122 An XFS filesystem has up to three parts: a data section, a log 123 section, and a real-time section. The real-time section is 124 optional, and the log section can be separate from the data 125 section or contained within it. 126 127 mtpt=mountpoint 128 Use with the "dmapi" option. The value specified here will be 129 included in the DMAPI mount event, and should be the path of 130 the actual mountpoint that is used. 131 132 noalign 133 Data allocations will not be aligned at stripe unit boundaries. 134 135 noatime 136 Access timestamps are not updated when a file is read. 137 138 norecovery 139 The filesystem will be mounted without running log recovery. 140 If the filesystem was not cleanly unmounted, it is likely to 141 be inconsistent when mounted in "norecovery" mode. 142 Some files or directories may not be accessible because of this. 143 Filesystems mounted "norecovery" must be mounted read-only or 144 the mount will fail. 145 146 nouuid 147 Don't check for double mounted file systems using the file system uuid. 148 This is useful to mount LVM snapshot volumes. 149 150 uquota/usrquota/uqnoenforce/quota 151 User disk quota accounting enabled, and limits (optionally) 152 enforced. Refer to xfs_quota(8) for further details. 153 154 gquota/grpquota/gqnoenforce 155 Group disk quota accounting enabled and limits (optionally) 156 enforced. Refer to xfs_quota(8) for further details. 157 158 pquota/prjquota/pqnoenforce 159 Project disk quota accounting enabled and limits (optionally) 160 enforced. Refer to xfs_quota(8) for further details. 161 162 sunit=value and swidth=value 163 Used to specify the stripe unit and width for a RAID device or 164 a stripe volume. "value" must be specified in 512-byte block 165 units. 166 If this option is not specified and the filesystem was made on 167 a stripe volume or the stripe width or unit were specified for 168 the RAID device at mkfs time, then the mount system call will 169 restore the value from the superblock. For filesystems that 170 are made directly on RAID devices, these options can be used 171 to override the information in the superblock if the underlying 172 disk layout changes after the filesystem has been created. 173 The "swidth" option is required if the "sunit" option has been 174 specified, and must be a multiple of the "sunit" value. 175 176 swalloc 177 Data allocations will be rounded up to stripe width boundaries 178 when the current end of file is being extended and the file 179 size is larger than the stripe width size. 180 181 182sysctls 183======= 184 185The following sysctls are available for the XFS filesystem: 186 187 fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1) 188 Setting this to "1" clears accumulated XFS statistics 189 in /proc/fs/xfs/stat. It then immediately resets to "0". 190 191 fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000) 192 The interval at which the xfssyncd thread flushes metadata 193 out to disk. This thread will flush log activity out, and 194 do some processing on unlinked inodes. 195 196 fs.xfs.xfsbufd_centisecs (Min: 50 Default: 100 Max: 3000) 197 The interval at which xfsbufd scans the dirty metadata buffers list. 198 199 fs.xfs.age_buffer_centisecs (Min: 100 Default: 1500 Max: 720000) 200 The age at which xfsbufd flushes dirty metadata buffers to disk. 201 202 fs.xfs.error_level (Min: 0 Default: 3 Max: 11) 203 A volume knob for error reporting when internal errors occur. 204 This will generate detailed messages & backtraces for filesystem 205 shutdowns, for example. Current threshold values are: 206 207 XFS_ERRLEVEL_OFF: 0 208 XFS_ERRLEVEL_LOW: 1 209 XFS_ERRLEVEL_HIGH: 5 210 211 fs.xfs.panic_mask (Min: 0 Default: 0 Max: 127) 212 Causes certain error conditions to call BUG(). Value is a bitmask; 213 AND together the tags which represent errors which should cause panics: 214 215 XFS_NO_PTAG 0 216 XFS_PTAG_IFLUSH 0x00000001 217 XFS_PTAG_LOGRES 0x00000002 218 XFS_PTAG_AILDELETE 0x00000004 219 XFS_PTAG_ERROR_REPORT 0x00000008 220 XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010 221 XFS_PTAG_SHUTDOWN_IOERROR 0x00000020 222 XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040 223 224 This option is intended for debugging only. 225 226 fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1) 227 Controls whether symlinks are created with mode 0777 (default) 228 or whether their mode is affected by the umask (irix mode). 229 230 fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1) 231 Controls files created in SGID directories. 232 If the group ID of the new file does not match the effective group 233 ID or one of the supplementary group IDs of the parent dir, the 234 ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl 235 is set. 236 237 fs.xfs.inherit_sync (Min: 0 Default: 1 Max: 1) 238 Setting this to "1" will cause the "sync" 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_nodump (Min: 0 Default: 1 Max: 1) 243 Setting this to "1" will cause the "nodump" 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_noatime (Min: 0 Default: 1 Max: 1) 248 Setting this to "1" will cause the "noatime" 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.inherit_nosymlinks (Min: 0 Default: 1 Max: 1) 253 Setting this to "1" will cause the "nosymlinks" flag set 254 by the xfs_io(8) chattr command on a directory to be 255 inherited by files in that directory. 256 257 fs.xfs.rotorstep (Min: 1 Default: 1 Max: 256) 258 In "inode32" allocation mode, this option determines how many 259 files the allocator attempts to allocate in the same allocation 260 group before moving to the next allocation group. The intent 261 is to control the rate at which the allocator moves between 262 allocation groups when allocating extents for new files. 263