LVM on NetBSD/i386 v6.1.4

[Ib-Michael Martinsen <i.m.martinsen%gmail.com@localhost>]

Dear list-members.

I have been trying out LVM on a vanilla NetBSD v6.1.4 installation.
So far it is looking good although I have experienced a few
problems.

For now I am able to create and use physical volumes, volume groups
and simple linear logical volumes, but whenever I try to create a
mirror LV or a snapshot LV, I get the following errors:



root:/root # lvm lvcreate -L 2g -n lv00 vg00
  Logical volume "lv00" created

root:/root # lvm lvcreate -L 2g -n lv01 -m 1 --mirrorlog core vg00
  Can't expand LV lv01: mirror target support missing from kernel?
  Aborting. Failed to activate new LV to wipe the start of it.

root:/root # lvm lvcreate -v -L 2g -n lv01 -m 1 --mirrorlog core vg00
    Setting logging type to core
    Finding volume group "vg00"
    Archiving volume group "vg00" metadata (seqno 17).
    Creating logical volume lv01
    Creating logical volume lv01_mimage_0
    Creating logical volume lv01_mimage_1
    Creating volume group backup "/etc/lvm/backup/vg00" (seqno 18).
    Found volume group "vg00"
  Can't expand LV lv01: mirror target support missing from kernel?
  Aborting. Failed to activate new LV to wipe the start of it.
    Found volume group "vg00"
    Found volume group "vg00"
    Creating volume group backup "/etc/lvm/backup/vg00" (seqno 19).

root:/root # lvm lvconvert -v -m 1 --mirrorlog core lv00
  mirror: Required device-mapper target(s) not detected in your kernel
  Run `lvconvert --help' for more information.

root:/root # lvm lvconvert -v -s lv00 snap00
    Setting chunksize to 8 sectors.
  snapshot: Required device-mapper target(s) not detected in your kernel
  Run `lvconvert --help' for more information.



Google'ing for "Required device-mapper target(s) not detected in your
kernel" I found the following page

http://www.novell.com/support/kb/doc.php?id=7010069

and although the page deals with a Linux LVM problem, it looks pretty
much the same to me. The page states:



The usual behavior of lvm2 command is to load the necessary module for
the requested action automatically.  In case of creating a snapshot
device this would be dm-snapshot or for pvmove it loads dm-mirror. The
version of lvm2 in question does not load the required modules and
thus the command fails.

On systems where the update cannot be installed immediately the
interim solution is to load the modules manually using the modprobe
command:

    modprobe dm-snapshot
    modprobe dm-mirror



NetBSD modstat shows:

root:/root # modstat
NAME             CLASS      SOURCE     REFS  SIZE     REQUIRES
...
<stuff deleted>
...
cx24227          driver     builtin    1     -        iic
cxdtv            driver     builtin    0     -        tvpll,nxt2k,lg3303,pci
dm               driver     filesys    0     19752    -
drm              misc       builtin    10    -        pci
dtv              driver     builtin    0     -        -
...
<stuff deleted>
...
root:/root # 



It seems that the device-mapper module is loaded but the dm-mirror
and dm-snapshot modules are not. I am unable to find these modules
anywhere on the filesystem.

Do I have to build these modules myself, build a new kernel or take
other actions to be able to create mirror and snapshot LVs or is
mirror and snapshot LVs not supported in NetBSD?



Assuming it is possible to generate (and use) mirror LVs, does anybody
have any thoughts of RAIDframe RAID1 compared to LVM mirroring as a
mean to ensure greater data safety?

To me the LVM mirroring seems to be the most flexible method, but am I
missing something?



Btw, I remember reading that snapshot LVs are not supported in
NetBSD. What is the problem and the prospects for a solution?

Kind regards
  Ib-Michael
-- 
Email: i.m.martinsen(at)gmail.com
Running NetBSD/i386 v6.0

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