Re: gpart, bsdlabel and fdisk

On Oct 22, 2009, at 10:09 AM, Aristedes Maniatis wrote:

> On 22/10/09 6:01 PM, Scot Hetzel wrote:
>> http://wiki.freebsd.org/RootOnZFS
>>
>> If anyone notices a problem with them, either let me know or update
>> the wiki page.
>
> That's very helpful, thanks Scot. It raises some questions:
>
> * you don't have the instruction to perform "echo 'a 1' | fdisk -f  
> - /dev/ad4" which Robert recommends
Shouldn't be needed if you use gpart. (Note: I haven't actually read  
the guides, but fdisk and gpart are both partitioning software, and I  
don't see why you'd need *both*. I've made several installs without  
ever touching fdisk, all ZFS only.)
>
> * Robert recommends GPT as the "easiest way to get ZFS on root  
> working". Your instructions seem to lean more toward MBR "The  
> advantage of using a MBR disk is that you can still dual boot with  
> other Operating Systems.". Are there any downsides of using MBR  
> which should be explained?
The biggest downside is the 2TB partition limit, both in size and  
offset. Larger disks (including HW RAID arrays) and you can't use MBR  
(without wasting space, of course).
>
> * you write LOADER_ZFS_SUPPORT=YES to src.conf, while previous  
> instruction in this thread had it written to make.conf
Doesn't matter, both are used for /usr/src; ports however doesn't read  
src.conf.

> As a feature request it would be great if gpart supported "-s all"  
> and made "-b" optional so that the next add starts at the beginning  
> of the first free space.
It's already supported, swap the last command for e.g.:
gpart add -t freebsd-zfs ad0 # Automatically fills the rest of the  
disk with a partition starting at the first free offset

Regards,
Thomas