Booting from ZFS raidz

[Doug Rabson]

I've been working on adding raidz and raidz2 support to the boot code  
and I have a patch which could use some testing if anyone here is  
interested. This http://people.freebsd.org/~dfr/ 
raidzboot-17122008.diff adds support for raidz and raidz2. The easiest  
way to prepare a bootable pool is to put a GPT boot partition on each  
disk that will make up the raidz pool and install gptzfsboot on the  
boot partition of every drive.

You can boot from any of the drives and as long as the BIOS can see  
enough drives you should be able to boot. The boot code supports  
booting from degraded pools and pools where some of the data is  
corrupt (as long as it has enough data available to repair the problem).

Currently the ZFS kernel code refuses to allow you to set the bootfs  
pool property on raidz pools (because Solaris can't boot from them).  
This means that you are limited to booting from the root filesystem of  
the pool for now (it shouldn't be hard to relax this restriction). The  
root filesystem of the pool should contain a directory /boot with the  
usual contents which must include a /boot/loader which was built with  
the 'LOADER_ZFS_SUPPORT' make option.