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Re: boot disk has two MBR partitions
On 1 Mar 2013 at 14:46, Saifi Khan wrote:
> On Sat, 23 Feb 2013, David Lord wrote:
> > 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:
> The 'mbrlabel' command helped insert the 2nd MBR partition
> entry in the disklabel.
> However, the wrong size was picked by mbrlabel (wonder why)
> and i had to edit the 'disklabel' entry from the information
> gleaned from 'fdisk' output.
> > 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.
> Does disk geometry, the CHS remapping and subsequent
> translation have any impact on the 'fsck' performance. ?
but I don't run fsck so often that it concerns me.
> >> 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".
> Would appreciate, if you could share an example where 'raw'
> device would be useful.
This is something that usally appears in the relevant man page
for the program you are using.
> >> 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.
> currently running netbsd-current (20120220 snapshot).
> i have had two freeze ups in the last 2 days, when i had to
> hold the 'power' button to switch off the laptop.
> On power cycling the device, on both occassions, i had to
> run 'fsck' manually to restore blocks, clean up etc.
I's rare for me to need to use fsck. After a crash requiring
reboot I see entries in /var/log/messages:
"/netbsd: /: replaying log to disk"
Were your partitions created manually?
Currently my systems have ffsv2 partitions either auto created
at install, using "newfs -O", or by using "ffsk_ffs -c 4" for
/etc/fstab entries have the "log" option, eg.
/dev/wd0a / ffs rw,log 1 1
/dev/wd0h /var ffs rw,log 1 2
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