# The 3MB guess is semi-arbitrary, but we've been informed that
# Lustre, for example, uses 1MB, so guess higher than that, at least.
-block_size=$(python -c \
+block_size=$(bup-python -c \
"import os; print getattr(os.stat('.'), 'st_blksize', 0) or $mb * 3") \
|| exit $?
data_size=$((block_size * 10))