Doc: Clusters from Scratch: Improve DRBD walkthrough
- Remove syncer section, which was made obsolete in DRBD 8.4. Move verify-alg to net section.
- Use new-style configuration instead of legacy 8.4-style. These changes aren't necessary but seem like best practices (although the user guide itself becomes inconsistent later, reverting to what it calls the old style at times).
- Use device minor 1 instead of device /dev/drbd1.
- Move protocol C to the net section where it belongs.
- Assign explicit an node-id to each node.
- Use a connection section instead of specifying addresses in on <host> sections.
- Quote strings.
- Ref: https://linbit.com/drbd-user-guide/drbd-guide-9_0-en/#s-drbdconf-example, especially Listings 2 and 4 and the bullet points beneath.
- Integrate with Pacemaker fencing.
- Use fencing resource-and-stonith.
- Use handlers for fence-peer and unfence-peer.
- Note: The DRBD user guide instructs to use the handler outdate-peer /sbin/kill-other-node.sh. But that script does not exist, and the DRBD source code comments say outdate-peer was replaced by fence-peer years ago. I'm using the settings from the fencing resource-only description. The crm-fence-peer.9.sh script seems to have at least been designed to work with fencing resource-and-stonith.
Signed-off-by: Reid Wahl <nrwahl@protonmail.com>