Re: boot disk has two MBR partitions

["David Lord" <netbsd%lordynet.org@localhost>]

On 23 Feb 2013 at 20:18, Saifi Khan wrote:

> 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 ?
> 

The NetBSD part of the disk is usually split into partitions

ID mount point
a: /
b: swap
c: NetBSD partitions
d: whole disk
e: /usr
f: /tmp
g: /var
....
m:

Having many mountable partitions used to have an advantage
after a major system crash in that some would be left clean
which reduced time spent by fsck. With current WAPBL the
journal is replayed after a crash which gives a fast 
recovery.

> 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 ?

The 'raw' devices have to be used in some cases but unless 
you are sure use the 'wd" rather than "rwd".

> 3. does fsck like utility perform better when one has slice with BSD 
> partitions rather than straight DOS like partition ?

DOS fat partitions become fragmented and can run out of
allocation units so require regular defragmentation as the
partition becomes full.

Fsck is not normally required on NetBSD ffs partitions.


David