My plan is to use "cp -p -R" to make the backup

NAME
xfs_growfs, xfs_info - expand an XFS filesystem

SYNOPSIS
xfs_growfs [ -dilnrxV ] [ -D size ] [ -e rtextsize ]
[ -L size ] [ -m maxpct ] [ -t mtab ]
[ -R size ] mount-point
xfs_info [ -t mtab ] mount-point

DESCRIPTION
xfs_growfs expands an existing XFS filesystem (see xfs(5)). The mount-
point argument is the pathname of the directory where the filesystem is
mounted. The filesystem must be mounted to be grown (see mount(8)).
The existing contents of the filesystem are undisturbed, and the added
space becomes available for additional file storage.

xfs_growfs is most often used in conjunction with logical volumes (see
lvm(8) ). However, it can also be used on a regular disk partition,
for example if a partition has been enlarged while retaining the same
starting block.

PRACTICAL USE
Filesystems normally occupy all of the space on the device where they
reside. In order to grow a filesystem, it is necessary to provide
added space for it to occupy. Therefore there must be at least one
spare new disk partition available. Adding the space is often done
through the use of a logical volume manager.