ZFS boot

[Danny Braniss]

> > > > so can Freebsd boot off a ZFS root? in stable? current? ...
> > > 
> > > boot0 doesn't apply here; it cares about what's at sector 0 on the
> > > disk, not filesystems.
> > > 
> > > boot2/loader does not speak ZFS -- this is why you need the /boot UFS2
> > > partition.  This is an annoyance.
> > > 
> > > For the final "stage/step", vfs.root.mountfrom="zfs:mypool/root" in
> > > loader.conf will cause FreeBSD to mount the root filesystem from ZFS.
> > > This works fine.
> > 
> > so the answer is:
> > 	yes, if you have only one disk.
> > 	no, if you have ZFS over many disks
> > 
> > because I see no advantage in the springboard solution where ZFS is used to
> > cover several disks.
> > 
> > I'm asking, because I want to deploy some zfs fileservers soon, and so
> > far the solution is either PXE boot, or keep one disk UFS (or boot off a USB)
> > Today's /(root+usr) is somewhere between .5 to 1Gb(kernel+debug+src),
> > and is readonly, so having 1 disk UFS seems to be a pitty.
> 
> Hold on a minute.  "One disk" has nothing to do with the filesystem.
> You asked if FreeBSD could boot off of a specific filesystem, and I
> answered that -- I didn't state anything about disk counts.  Now you're
> changing the focus.  :-)
> 
not intentionaly, but once you mention boot0/2, bsdlabel, slice/partition ...

/OT
Initially, I was not thrilled with ZFS, but once you cross the
few hundred gigabyte filesystems UFS is impractical, and though old sysadmins
will have to be re-educated (zfs catch-all-commands, instead of mount/fsck/export/blah...)
it is the (only?) way for the new-terrabyte-world. So having bitten the bullet,
and doing some experiments i'm stuck as to what to do with /
OT/

> I'm pretty sure FreeBSD can boot off of gmirror setups (see above,
> boot2/loader should work off of gmirror), which means >1 disk.  You
> do not have to gmirror the entire disk, you can gmirror just a slice
> (AFAIK).
but gmirror is not ZFS, and yes it can, why not.

> 
> I think (hope?) you can use the "remaining" (e.g. non-UFS/non-gmirror)
> part of the 2nd disk for ZFS as well, otherwise the space would go
> to waste.  The "Root on ZFS configuration" FreeBSD ZFS Wiki page
> seems to imply you can.

The idea is to used the 'free/remaining' as part of the BIG ZFS 'array'

[ED note : I've highjacked the 'Re: continuous backup solution for FreeBSD']

To Matt:
	since 'small' nowadays is big enough to hold /, what advantages are there
in having root split up?
also, having this split personality, what if the disk goes? the hammer/zfs
is probably raided ...
[btw, having a small-boot-partition brings back bad memories: the first thing 
I did on a new Compact was boot it diskless, repartition the disk, newfs, and
I could no longer boot it :-) - part of the BIOS was there]

To Doug:
	> ZFS boot is coming.
great! any time estimate?, just curious, no preasure :-)

some food for thought:
In the past raid 5 would reduce the throughput conciderably, though
nowadays it's hardly notisable, so I guess my reluctance to having
a swap partition raided is gone.

danny