class Aruba::Platforms::DetermineDiskUsage

Determinate disk usage

@private

Public Instance Methods

Source

# File lib/aruba/platforms/determine_disk_usage.rb, line 11
def call(paths)
  size = paths.flatten.sum { |path| minimum_disk_space_used path }

  FileSize.new(size)
end

Private Instance Methods

minimum_disk_space_used (path)

Source

# File lib/aruba/platforms/determine_disk_usage.rb, line 49
def minimum_disk_space_used(path)
  # TODO: replace Aruba.config.physical_block_size
  # with something like Aruba.config.fs_allocation_unit
  dev_bsize = Aruba.config.physical_block_size

  stat = File::Stat.new(path.to_s)

  blocks = stat.blocks
  return blocks * dev_bsize if blocks

  typical_fs_unit = 4096
  typical_dev_bsize = 512 # google dev_bsize for more info

  block_multiplier = typical_fs_unit / typical_dev_bsize
  fs_unit_size = dev_bsize * block_multiplier
  fs_units = (stat.size + fs_unit_size - 1) / fs_unit_size
  fs_units = 1 if fs_units.zero?
  fs_units * fs_unit_size
end

Report minimum disk space used

This estimates the minimum bytes allocated by the path.

E.g. a 1-byte text file on a typical EXT-3 filesystem takes up 4096 bytes (could be more if it was truncated or less for sparse files).

Both ‘File::Stat` and the `stat()` system call will report 8 `blocks` (each “usually” represents 512 bytes). So 8 * 512 is exactly 4096 bytes.

(The “magic” 512 bye implied makes the value of “blocks” so confusing).

Currently Aruba allows you to set what’s called the ‘physical_block_size`, which is a bit misleading - it’s the “512” value. So if you somehow have a “filesystem unit size” of 8192 (instead of a typical 4KB), set the ‘physical_block_size` to 1024 (yes, divide by 8: 8192/8 = 1024).

Ideally, Aruba should provide e.g. ‘Aruba.config.fs_allocation_unit` (with 4096 as the default), so you wouldn’t have to “divide by 8”.

(typical_fs_unit / typical_dev_bsize = 4096 / 512 = 8)

@return [Integer]

Total bytes allocate

TODO: this is recommended over the above “blocks”