Re: dk for z/lvm volumes?

[Greg Troxel <gdt%lexort.com@localhost>]

Staffan Thomén <duck%shangtai.net@localhost> writes:

I should point out that I am underclued on zfs and windows both.

> I recently wanted to set up backup of a (snapshot of a) zvol that I
> had exported via iscsi to a windows machine, and got stumped because
> windows didn't just create a ntfs filesystem on the volume, it also
> added a partition table and so mount_ntfs and ntfs-3g couldn't find
> the filesystem on it.

Once you export a zvol via iscsi, then it makes sense to methat the system
attaching it sees it as a disk drive.

> I couldn't coax dkctl to create dk devices for the gpt on the volume,
> and dkctl seems like a bit of a mismatch for creating arbitrary dk:s
> anyway as it seems mostly directed at bare drives (cache settings
> etc).

From the NetBSD point of view there is a zvol, and you are letting iscsi
manage it.  So there's nothing to tell netbsd to read a gpt/mbr and
deal.

> My other thought was using vnconfig, but that doesn't seem like the
> right tool either.

It seems sensible to me; vnconfig takes a file and tells the system to
treat it like a disk.   I don't know if doing vnconfig on a zvol works
right, but it doesn't feel broken.  Once you do this then if there is a
gpt then the partitions should show up as dkN, I'd expect.

The other thing you can do is export the zvol snapshot via iscsi and use
an iscsi initiator on netbsd to mount it.  I suspect this amounts to
about the same thing as vnconfig.

> This left me with a couple of questions, is dk the right fit for
> getting at partitions on logical volumes? Could a tool be written that
> does this so we wouldn't have to load down dkctl with features that
> aren't really related to disks or is dk* not the right device and a
> new driver is needed?  Have I just missted something?

I think you are only troubled by not wantting to use vnconfig, whose
purpose is to turn a file into a disk, so that you can then do all the
things with it that you normally do with disks.