[DRBD-user] "To resolve this both sides have to support at least protocol" after upgrade

Lars Ellenberg lars.ellenberg at linbit.com
Thu Dec 9 21:32:27 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 Fri, Dec 10, 2010 at 06:45:15AM +1100, Tim Sharpe wrote:
> Hi Lars,
> Thanks for getting back to me.
> A couple of questions though.  Why would it need protocol 91 if they
> both supported protocol 90 and why would this issue only show up on
> one of the resources on this box while the other 15 resources ran
> fine?

Because it's a bug?

Because it's a racy bug,
both sides have to agree on the result of the sync handshake,
one "aware" side is enough to detect it,
but you need both sides "aware" of the issue to resolve it.

Prior versions would not even have detected it, but more or less
silently skipped the resync (they would have logged some warning about
no resync, but bits in bitmap), because of the identical (ignore the
right most bit) "current" UUIDs, even though there have been "dirty"
bits in the bitmap.

: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

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