If you resize your volume and the size or available space doesn’t match what you expected, there may be several reasons why:

• The size of the filesystem that df reports may be slightly less than the total disk size because some amount of the disk is reserved for filesystem metadata.

• The sum of used and available space will be slightly less than the reported total size because a small amount of space is reserved for the root user (typically 5% by default), and df does not report this space.

  You can modify the reserved filesystem blocks and other filesystem parameters with tune2fs for ext4 filesystems and xfs_io for XFS filesystems.

• Different tools report size in different units, like gigabytes (1 GB = 1000 bytes) or gibibytes (1 GiB = 1024 bytes). For example, df -h reports size in powers of 1024, like GiB, and df -H reports sizes in powers of 1000, like GB. 500 GiB is approximately 536 GB.