(resolves #2) The global parity is obtained while packing blocks.

Benchmarks in my computer reported better performance:

Before:
Size: 1,612,393 KBytes ( 1.6GB )

1) 17.410 secs
2) 17.376 secs
3) 19.392 secs
4) 16.539 secs

After:
Size: 1,612,393 KBytes ( 1.6GB )

1) 15.501 secs
2) 14.208 secs
3) 13.694 secs
4) 14.077 secs