dangerously dedicated physical disks.

atar atar.yosef at gmail.com
Sun Sep 22 15:03:37 UTC 2013

Thank you very much about your efforts to explain me in detailed the  
'dangerous dedicated' term.



Warren Block <wblock at wonkity.com> wrote:

> On Sun, 22 Sep 2013, atar wrote:
>> During the reading of the FreeBSD handbook, I've encountered at the  
>> term 'dangerously dedicated' regarding physical disks and the author of  
>> this chapter in the FreeBSD handbook didn't think this term need more  
>> clarity. so for newbies like me in the FreeBSD world I want to ask:  
>> what's the 'dangerously dedicated' term meaning by?
> The term refers to a disk partitioned with only the BSD disklabel  
> partition table:
>    disk ada0
>      partition "a" (ada0a, /)
>      partition "b" (ada0b, swap)
>      partition "d" (ada0d, /var)
>      partition "e" (ada0e, /tmp)
>      partition "f" (ada0f, /usr)
> It's "dangerous" because that partitioning format is rare outside of  
> BSD-based systems.  Disk utilities may not recognize it, and could
> damage it.
> Most of the rest of the world used MBR partitioning, which allowed up to  
> four MBR partitions (called "slices" by FreeBSD) per disk.
> Since four slices is not enough for the standard FreeBSD disk layout,  
> with /, swap, /var, /tmp, and /usr, the standard procedure is to use MBR  
> partitioning, with the MBR partitions ("slices") being sub-partitioned  
> by a BSD disklabel.
>    disk ada0
>      MBR slice 1 (ada0s1)
>        partition "a" (ada0s1a, /)
>        partition "b" (ada0s1b, swap)
>        partition "d" (ada0s1d, /var)
>        partition "e" (ada0s1e, /tmp)
>        partition "f" (ada0s1f, /usr)
>     MBR slice 2 (ada0s2)
>        ...
> Yes, one partition format inside another.  It only seems complicated  
> because it is.
> GPT is the new partitioning format, which makes things much simpler by  
> being capable of up to 128 partitions in the standard configuration.  
> With GPT, there is no reason to use BSD disklabels at all.
>    disk ada0
>      GPT partition 1 (ada0p1, bootcode)
>      GPT partition 2 (ada0p2, /)
>      GPT partition 3 (ada0p3, swap)
>      GPT partition 4 (ada0p4, /var)
>      GPT partition 5 (ada0p5, /tmp)
>      GPT partition 6 (ada0p6, /usr)
> Summary: "Dangerously dedicated" partitioning has no unique advantages.  
> Use GPT when possible, use MBR/disklabel when necessary.

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