continuous backup solution for FreeBSD

[Mike Meyer]

On Sat, 11 Oct 2008 04:24:31 -0700
Jeremy Chadwick <koitsu at FreeBSD.org> wrote:
> > 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.  :-)
> 
> 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).
>
> 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.

You mean like this:

bhuda% gmirror status
       Name    Status  Components
mirror/boot  COMPLETE  ad0s1a
                       ad1s1a
bhuda% zpool status
  pool: internal
 state: ONLINE
 scrub: none requested
config:

	NAME        STATE     READ WRITE CKSUM
	internal    ONLINE       0     0     0
	  mirror    ONLINE       0     0     0
	    ad0s1d  ONLINE       0     0     0
	    ad1s1d  ONLINE       0     0     0

errors: No known data errors

Yes, I don't get the benefits of having /boot on a zfs partition, but
I do get the benefits of having it on a mirror: automatic duplication,
reads from either device, and I can use either device stand-alone if I
break the mirror.

Note that FreeBSD booting from a gmirror'ed partition/disk can't boot
from the gmirror device - boot doesn't understand gmirror. It can,
however, boot from any of the devices participating in the mirror. The
mirror device appears after the kernel is loaded.

Given that I have to have a separate boot partition, having swap
partitions on the drives is a win compared to swapping to a zvol. I'm
going to investigate putting /boot on an SSD of some kind so that ZFS
can have the entire disk.

	<mike
-- 
Mike Meyer <mwm at mired.org>		http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.

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