[DRBD-user] DRBD and LVM Snapshot with 2 nodes configuration

Todd Denniston Todd.Denniston at ssa.crane.navy.mil
Wed Apr 7 23:00:40 CEST 2004

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

What about a slight modification to your procedure
Lars get your clue stick, I bet you'll need to beat me with it :)

Andreas Semt wrote:
> Okay, now I have two possible ways to go, but can I suggest a third way
> (cause I won't use LVM2, so only one way left ...)?
> The situation is:
> nodeA (Heartbeat and drbd active), nodeB (Heartbeat and drbd standby).
> To make a clean and consistent snapshot i will do following (all on nodeB!):
a0) on Node A at 01:59 per cron { while [ time != 0201 ]; do sync;done }
> a) stop heartbeat (at 02.00 pm per cron for example), i.e. that means
>     for heartbeat: "nodeB is dead!, i am the only one left!"
> b) -> <not right>
> c) shut down drbd (or heartbeat shut down drbd)
Now drbd knows nothing about the other node.
c1) violate a drbd tenet:
    mount -t ext2 -o ro /dev/device_under_drbd /mnt_point
    # perhaps a thinko here, you do not want the 
    #journal ran because that would change the under device 
    #with out drbd knowing. (assumption ext3 filesystem)
c2) make backup from now snapped device
c3) umount /mnt_point
c4) skip to (e)

> d) "lvcreate snapshot" for the drbd block devices / do anything with the
>     snapshot
> e) bring drbd up again and start heartbeat (or heartbeat brings drbd up
>     again)
> f) synch between nodeA to nodeB will be started

Todd Denniston
Crane Division, Naval Surface Warfare Center (NSWC Crane) 
Harnessing the Power of Technology for the Warfighter

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