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xfs_info(8) System Manager's Manual xfs_info(8)

xfs_info - display XFS filesystem geometry information

xfs_info [ -t mtab ] [ mount-point | block-device | file-image ]
xfs_info -V

xfs_info displays geometry information about an existing XFS filesystem. The mount-point argument is the pathname of a directory where the filesystem is mounted. The block-device or file-image contain a raw XFS filesystem. The existing contents of the filesystem are undisturbed.

Specifies an alternate mount table file (default is /proc/mounts if it exists, else /etc/mtab). This is used when working with filesystems mounted without writing to /etc/mtab file - refer to mount(8) for further details. This option has no effect with the block-device or file-image parameters.
Prints the version number and exits. The mount-point argument is not required with -V.

Understanding xfs_info output.

Suppose one has the following "xfs_info /dev/sda" output:

meta-data=/dev/pmem0             isize=512    agcount=8, agsize=5974144 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=1, rmapbt=1
         =                       reflink=1
data     =                       bsize=4096   blocks=47793152, imaxpct=25
         =                       sunit=32     swidth=128 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=23336, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

Here, the data section of the output indicates "bsize=4096", meaning the data block size for this filesystem is 4096 bytes. This section also shows "sunit=32 swidth=128 blks", which means the stripe unit is 32*4096 bytes = 128 kibibytes and the stripe width is 128*4096 bytes = 512 kibibytes. A single stripe of this filesystem therefore consists of four stripe units (128 blocks / 32 blocks per unit).

mkfs.xfs(8), md(4), lvm(8), mount(8).