Synnefo » snf-ganeti

from ganeti import constants

def LvmExclusiveCheckNodePvs(pvs_info):

  """Check consistency of PV sizes in a node for exclusive storage.

  @type pvs_info: list

  @param pvs_info: list of L{LvmPvInfo} objects

  @rtype: list

  @return: A list of error strings described the violation found, or an empty

      list if everything is ok

  """

  errmsgs = []

  sizes = [pv.size for pv in pvs_info]

  # The sizes of PVs must be the same (tolerance is constants.PART_MARGIN)

  small = min(sizes)

  big = max(sizes)

  if LvmExclusiveTestBadPvSizes(small, big):

    m = ("Sizes of PVs are too different: min=%d max=%d" % (small, big))

    errmsgs.append(m)

  return errmsgs

def LvmExclusiveTestBadPvSizes(small, big):

  """Test if the given PV sizes are permitted with exclusive storage.

  @param small: size of the smallest PV

  @param big: size of the biggest PV

  @return: True when the given sizes are bad, False otherwise

  """

  # Test whether no X exists such that:

  #   small >= X * (1 - constants.PART_MARGIN)  and

  #   big <= X * (1 + constants.PART_MARGIN)

  return (small * (1 + constants.PART_MARGIN) <

          big * (1 - constants.PART_MARGIN))