< 	o Store disk pages with no alignment/padding?
>
> 	  This involves having the user-specified order of columns
> 	  be different from the physical order.  SELECT * would
> 	  need to reorder the physical values to match the
> 	  user-specified ordering.
>
> 	o Store disk pages with no alignment/padding?
>
> 	  This necessitates adding CPU-required padding when moving
> 	  rows from disk to memory.
>
>
> 	  http://archives.postgresql.org/pgsql-hackers/2006-09/msg00848.php
>