[DRBD-user] strange split-brain problem

Andrew Gideon ag928272 at gideon.org
Tue Dec 7 16:39:31 CET 2010

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

On Tue, 07 Dec 2010 14:29:39 +0100, Felix Frank wrote:

> Node A is primary and marks some extents as hot.

Is this just a matter of timing, or were they hot because the writes 
occurred while node B was down?  I'm guessing the former.  If the latter, 
then the activity log would grow unbounded while one node was down.

Have I understood correctly?

I'm puzzled at how recovery and synchronization is occurring after a 
failure.  In the scenario described by klaus.mailinglists at pernau.at, node 
B has been down.  So where is the benefit of syncing with it when node A 
returns to service?  Would that not roll the state of storage back to 
when node B failed?

I'm envisioning an extent that is the recipient of multiple writes over 
the time while B is down.  One is recent - leaving the extent "hot" - 
when node A goes down.

If the "hotness" causes that extent to be restored to the state stored on 
B, would that not roll that extent back several writes?

I assume that this doesn't actually happen, but I'm trying to understand 
how the mechanism involved works.



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