ZFS boot

[Xin LI]

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Hi, Matt,

Matthew Dillon wrote:
[...]
>     /boot can be as complex as boot2 allows.  There's nothing preventing
>     it from being RAIDed if boot2 supported that, and there's nothing
>     preventing it (once you had ZFS boot capabilities) from being ZFS
>     using a topology supported by boot2.  Having a sparate /boot allows
>     your filesystem root to use topologues boot2 would otherwise not
>     support.

I believe that it's a good idea to separate / from the zpool for other
file systems, or even use a UFS /.  My experience with ZFS on my laptop
shows that disk failures can be more easily fixed if there are some
utilities available in the UFS /, even when ZFS is used as /.  Another
issue with a ZFS / is that the snapshot rollback feature generally does
not work on / since it needs the mountpoint to be unmounted.

One thing that I found very useful is the new GPT boot feature on 8.0,
which also works on older BIOS because the protected MBR would deal with
the bootstrap to the actual GPT boot.  Now we have a 15-block sized
gptboot that can boot FreeBSD from UFS, however this 'boot' can be in
virtually any size that the BIOS supports, so we can embed more logic there.

Cheers,
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