Re: ZFS pool corrupted on upgrade of -current (probably sata renaming)

On Wed, Jul 15, 2009 at 03:19:30PM -0700, Freddie Cash wrote:
> 
> Hrm, you might need to do this from single-user mode, without the ZFS
> filesystems mounted, or the drives in use.  Or from a LiveFS CD, if /usr is
> a ZFS filesystem.
> 
> On our ZFS hosts, / and /usr are on UFS (gmirror).

I don't understand why you'd expect you could take an existing
container on a disk, like a FreeBSD slice with some sort of live data
within it, and just decide you're going to take a way one or more
blocks at the end to create a new container within it?

If you look at page 7 of the ZFS on-disk format document that was
recently mentioned, you'll see that ZFS stores 4 copies of it's "Vdev
label"; two at the front of the physical vdev and two at the end of
the Vdev, each of them apparently 256kb in length.  That's assuming
that ZFS doens't round down the size of the Vdev to some convienient
boundary.  It is going to get upset that the Vdev just shrunk out from
under it?

I've always thought of glabel as creating a new (named) container
within some existing physical or logical container.  This notion that
you can just create one inside an existing container with live data
seems dangerous.  Or at a minimum, depending on some other property of
the existing live data that would lead you to believe it can do
without it's last block.

louie