Booting from ZFS raidz

Nathanael Hoyle nhoyle at hoyletech.com
Thu Apr 16 11:25:43 PDT 2009


Ollivier Robert wrote:
> According to Ollivier Robert:
>   
>> with tank containing a raidz array, zpool refuses to set the property,
>> saying it is not available.  Using the same commandline on a mirror works.
>>     
>
> BTW all messages I've found on this subject assume (like the script does)
> that one can do installworld/installkernel.
>
> I can setup the whole gpt thing from livefs, even extracting all dists on
> the newly zfs pool manually by playing with livefs/dvd1 but it can not boot
> afterwards because / can not be found.
>
> I must have missed something...  I long for pcbsd setup with zfs support in
> fact I think :(
>   

To my knowledge, RAID-Z root (boot) pools are not supported.  I know 
that this is true for upstream (Solaris) ZFS, and unless the FreeBSD 
folks implemented it when I wasn't looking, you can't do it on FreeBSD 
either.  I believe the current implementation essentially reads 
"through" the mirror structure on a mirrored device and can find all of 
the data by "dumb" sequential reads on the first disk, just as it would 
with unpooled disks.  In the case of RAID-Z the boot loader would have 
to be far more intelligent in locating where to read the next block 
from.  It is my understanding that this is a planned future improvement 
(at least for upstream) but haven't heard any update on it in a while.

-Nathanael


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