def METHOD_NAME(size_in_bytes, default_part_size=DEFAULT_PART_SIZE):
    """Calculate the minimum part size needed for a multipart upload.
    Glacier allows a maximum of 10,000 parts per upload.  It also
    states that the maximum archive size is 10,000 * 4 GB, which means
    the part size can range from 1MB to 4GB (provided it is one 1MB
    multiplied by a power of 2).
    This function will compute what the minimum part size must be in
    order to upload a file of size ``size_in_bytes``.
    It will first check if ``default_part_size`` is sufficient for
    a part size given the ``size_in_bytes``.  If this is not the case,
    then the smallest part size than can accomodate a file of size
    ``size_in_bytes`` will be returned.
    If the file size is greater than the maximum allowed archive
    size of 10,000 * 4GB, a ``ValueError`` will be raised.
    """
    # The default part size (4 MB) will be too small for a very large
    # archive, as there is a limit of 10,000 parts in a multipart upload.
    # This puts the maximum allowed archive size with the default part size
    # at 40,000 MB. We need to do a sanity check on the part size, and find
    # one that works if the default is too small.
    part_size = _MEGABYTE
    if (default_part_size * MAXIMUM_NUMBER_OF_PARTS) < size_in_bytes:
        if size_in_bytes > (4096 * _MEGABYTE * 10000):
            raise ValueError("File size too large: %s" % size_in_bytes)
        min_part_size = size_in_bytes / 10000
        power = 3
        while part_size < min_part_size:
            part_size = math.ldexp(_MEGABYTE, power)
            power += 1
        part_size = int(part_size)
    else:
        part_size = default_part_size
    return part_size