boot disk has two MBR partitions

["Saifi Khan" <saifi.khan%fastpath.in@localhost>]

Hi:

Please excuse me for asking rather 'naive' question.

i've rtfm'd at
http://www.netbsd.org/docs/guide/en/netbsd.html

Now, i have a boot disk (NetBSD terminology) of 320 GB (SATA II). 

Booted my laptop with 'boot.iso' (NetBSD-current) and using the 'NetBSD' fdisk 
utility, i created two MBR partitions (NetBSD terminology) of the following 
size:
 partition no 1: 20 GB   (base system, src)
 partition no 2: 300 GB (pkgsrc, other sources, mails etc.)

i intend to setup 'ffs' on both the MBR partitions.

in the linux world, the disk would typically be '/dev/sda' and the two profound 
partitions would be
 /dev/sda1
 /dev/sda2

in the NetBSD scheme of things, the first disk is seen as 'wd0'. In that case, 
how would the two 'MBR partitions' be addressed as ?

i also have a couple of related questions:

1. what is the rationale behind using 'd' in BSD partition to represent the 
entire disk ? 
2. what is the significance of using two representations like wd0 and rwd0 ?
3. does fsck like utility perform better when one has slice with BSD partitions 
rather than straight DOS like partition ?

Thanks in advance for any pointers.

thanks
Saifi.