[DRBD-user] problem using lv as drbd backend device

Mia Lueng xiaozunvlg at gmail.com
Mon Oct 7 10:27:56 CEST 2013

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


I find a solution :
1. drbdadm sh-ll-dev drbd0  find drbd0's backend lv
2. map lv to dm-x ,   ls /sys/block/dm-x/holders    to find the frontend lv
3. dmsetup remove -f $frontlv



2013/10/7 Digimer <lists at alteeve.ca>

> On 06/10/13 23:26, Mia Lueng wrote:
> > I have built a drbd cluster. The storage setting is like the following:
> >
> > backend LV--->drbd0--->pv-->vg-->userlv
> >
> > That means I create a drbd device on a LV, and create a volume group on
> > drbd device again.
> >
> > In /etc/lvm/lvm.conf, I add a filter so that pvscan do not probe for the
> > backend LV.  This works fine on normal suitation.
> >
> > Now A is primary, and B is secondary.    Break the link of A's
> > storage(fc san), HA cluster will detect the error and failover the
> > resource from A to B. But the drbd resource  and filesystem can not be
> > stopped on A, so A will be reboot (due to stop fail handle) and B will
> > takeover all the resource. When A rejoin the cluster, the drbd resource
> > can not be start as secondary automatically: the backend LV can not be
> > attached to the drbd resource.
> >
> > vcs2:~ # lvs
> >   LV       VG     Attr   LSize    Origin Snap%  Move Log Copy%  Convert
> >   drbd0_lv drbdvg -wi-ao  800.00M
> >   oralv    oravg  -wi-a- 1000.00M
> > vcs2:~ # modprobe drbd
> > vcs2:~ # drbdadm up drbd0
> > 0: Failure: (104) Can not open backing device.
> > Command 'drbdsetup 0 disk /dev/drbdvg/drbd0_lv /dev/drbdvg/drbd0_lv
> > internal --set-defaults --create-device --on-io-error=pass_on
> > --no-disk-barrier --no-disk-flushes' terminated with exit code 10
> > vcs2:~ # fuser -m /dev/drbdvg/drbd0_lv
> > vcs2:~ # lvdisplay /dev/drbdvg/drbd0_lv
> >   --- Logical volume ---
> >   LV Name                /dev/drbdvg/drbd0_lv
> >   VG Name                drbdvg
> >   LV UUID                Np92C2-ttuq-yM16-mDf2-5TLE-rn5g-rWrtVq
> >   LV Write Access        read/write
> >   LV Status              available
> >   # open                 1
> >   LV Size                800.00 MB
> >   Current LE             200
> >   Segments               1
> >   Allocation             inherit
> >   Read ahead sectors     auto
> >   - currently set to     1024
> >   Block device           252:6
> >
> >
> > My solution is:
> > 1.restore the default configure of /etc/lvm/lvm.conf and run
> > pvscan/vgchange -ay to active the lv on drbd0(now on the backend lv) and
> > deactive it again.
> > 2. change the lvm.conf to cluster config and run pvscan/vgchange -ay
> again
> > 3. start drbd0 , attach the backend lv
> > 4. run drbdadm verify drbd0 on primary node.
> >
> > It does work.
> >
> > Have anyone a better solution? Thanks.
>
> I played with this same configuration and decided that the headache of
> LV under and over DRBD was not justified. I have instead used partition
> -> drbd -> lvm and life has been very much easier.
>
> --
> Digimer
> Papers and Projects: https://alteeve.ca/w/
> What if the cure for cancer is trapped in the mind of a person without
> access to education?
>
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