10.1 fresh install and 4k alignment

[Mark Martinec]

> None of the start sector numbers is a multiple of 8, neither are the
> end sectors a multiple of 8 minus 1.
> 
> So the pool uses a 4k block size but it starts on an odd multiple of 2k
> on the platter - do I see this correctly?
> [...]
> Is this a bug in the installer? Will I still have to layout the disks
> manually if I want 4k alignment? What's a good offset for the first
> partition in this case? Anything bigger than 34 that's a multiple of
> 8 - 40 or 64?

>>  "GPT partitions not 4k aligned by 10.1-RC1 installer"
>>  
>> https://lists.freebsd.org/pipermail/freebsd-stable/2014-October/080509.html

I consider a sensible alignment nowadays to be '-a 1m' for any
GPT partition, including freebsd-boot. If one is very short on space
and not on an SSD, one may save 0.5 MB by aligning freebsd-boot
on -a 512k and everything else on '-a 1m':

   gpart add -t freebsd-boot -a 1m -s 512k -i 1 ...
   gpart add -t freebsd-swap -a 1m  -i 2 ...
   ...

or:
   gpart add -t freebsd-boot -a 512k -s 512k -i 1 ...
   gpart add -t freebsd-swap -a 1m  -i 2 ...
   ...


Mark