[DRBD-user] Avoid split brain in a dual primary configuration with intelligent switches

Mario Giammarco mgiammarco at gmail.com
Tue Feb 10 15:24:32 CET 2009

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


Hello,
I am trying to build an iscsi san using drbd in a dual primary
configuration.

 I have read drbd documentation and I have not fully understood how it
handles the split brain.

My hardware is setup as this: two identical server with raid6. Each one has
4 ethernet cards, configured as two trunks.
Each trunk is connected to an hardware switch. The two switches are
"intelligent", so they have an ip each.

My idea (correct me if I am wrong) is this: when one primary finds that it
cannot talk to other primary it tries to ping switches.

If it cannot ping switches it means that all its ethernet cards or all
switches are broken so it shutdown itself.
If it can ping switches it means that other primary is broken so it tries to
stonith it.

After reconnection it is clear that the primary that cannot ping the
switches must resync with other one.

Can you say me if I can personalize the behaviour of drbd to follow these
rules? (dopd? peer-outdater?)
Can you say me if my rules are enough?
Can you say me if drbd already implements a better strategy and so my rules
are stupid?

Thank you in advance for any reply!

Mario
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