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: 6000) 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: 30000) 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.refcache_size (Min: 0 Default: 128 Max: 512) 176 Controls the size of the NFS refcache, which holds references 177 on files opened via NFS to improve performance. The value 178 is the maximum number of files which can be in the cache at 179 any one time. 180 181 fs.xfs.refcache_purge (Min: 0 Default: 32 Max: 512) 182 Controls the number of entries purged from the NFS refcache 183 every sync interval. 184 185 fs.xfs.inherit_sync (Min: 0 Default: 1 Max 1) 186 Setting this to "1" will cause the "sync" flag set 187 by the chattr(1) command on a directory to be 188 inherited by files in that directory. 189 190 fs.xfs.inherit_nodump (Min: 0 Default: 1 Max 1) 191 Setting this to "1" will cause the "nodump" flag set 192 by the chattr(1) command on a directory to be 193 inherited by files in that directory. 194 195 fs.xfs.inherit_noatime (Min: 0 Default: 1 Max 1) 196 Setting this to "1" will cause the "noatime" flag set 197 by the chattr(1) command on a directory to be 198 inherited by files in that directory. 199