gpart usage

[Andrey V. Elsukov]

On 24.05.2011 17:20, Victor Balada Diaz wrote:
> Ie, no 16 sector offset in it. So my question is... What's the proper way of
> doing a MBR + BSD label partition and where is it documented? what are the different
> bootcodes and when is needed each one?[1] 

gptboot is used for GPT scheme. It should be written to the partition
with type "freebsd-boot". And it searches in the GPT table partitions
with type "freebsd-ufs" to boot from.

gptzfsboot is also used for GPT, but it searches ZFS pools on the
partitions with type "freebsd-zfs".

zfsboot is used for MBR and BSD schemes to boot from ZFS.

> also, how do i know about offsets each partitioning scheme needs? shouldn't GEOM
> take care of it without user needing to know anything about it?

Usually you do not need to know anything about offsets.

> If i wanted to also align partition to 1 MB offsets so i can get better performance
> with advanced format drives and RAID controllers, what would be the best option?
> I guess that i would need to add the first freebsd-ufs partition starting at 1985
> sector, because 1 MB = 2048 512byte sector, and 63 are reserved for MBR scheme
> so 2048 - 63 = 1985. Is this right or i'm mistaken in something?

Yes, you are right.

> Seems that gpart man page only documents doing it with GPT and doesn't talk
> about alignment constraints, but i can't use GPT because i want to do it over
> gmirror and last sector is used by gpt and gmirror at the same time causing
> some warnings[2].

You can create GPT on top of your mirror. It will cause some warnings,
but all should work.

-- 
WBR, Andrey V. Elsukov

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