On Mon, Oct 20, 2008 at 1:27 PM, Federico Simoncelli
<federico.simoncelli@xxxxxxxxx> wrote:
> I confirm that the patch works fine. I just need to say that the
> two_node flag is required anyway:
>
> <cman two_node="1">
After some testing I discovered that we need a couple of patches to
achieve the behaviour we wanted.
Basically if you set two_node=1 the quorum is locked to 1 (no matter
what expected_votes you configure). I unlocked the quorum value with
the patch "cman-2.0.84-2node2expected.patch" (in attachment). Now we
can change the quorum using the expected_votes:
# cman_tool expected -e 2 && cman_tool status | grep Quorum
Quorum: 2
# cman_tool expected -e 1 && cman_tool status | grep Quorum
Quorum: 1
In the same patch I fixed what I believe is a bug. Basically in the
file /cman/daemon/cmanccs.c the values node_count and vote_sum are
computed only if expected_votes == 0 but those values are used
afterwards:
if (two_node) {
if (node_count != 2 || vote_sum != 2) {
To quickly verify the bug:
# cman_tool join -w -e 1
It should generate the error "two_node set but there are more than 2
nodes" on any cman version.
The second patch "cman-2.0.84-startupquorum.patch" is the init patch
to take advantage of the expected_votes and the quorum.
Using the following configuration:
# cat /etc/sysconfig/cman
CMAN_QUORUM_TIMEOUT=10
CMAN_PREJOIN_EXPECTED=2
CMAN_POSTJOIN_EXPECTED=1
Your cluster needs the quorum to be 2 (CMAN_PREJOIN_EXPECTED) within
10 seconds to start. No fencing (and no fencing loops) will be
performed if the quorum is less than CMAN_PREJOIN_EXPECTED. After the
join session the expected_votes are set back to 1
(CMAN_POSTJOIN_EXPECTED) and the quorum goes back to 1 too.
Comments are welcome,
--
Federico.
Attachment:
cman-2.0.84-2node2expected.patch
Description: Binary data
Attachment:
cman-2.0.84-startupquorum.patch
Description: Binary data
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