Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Thank you Digimer very much for your effort & time. Would you Please see the question below ? :) On Fri, Mar 14, 2014 at 4:44 PM, Digimer <lists at alteeve.ca> wrote: > On 14/03/14 05:34 AM, khaled atteya wrote: > >> A- In DRBD Users's guide , in explanation of "resource-only" which one >> of fencing policy , they said: >> >> "If a node becomes a disconnected primary, it tries to fence the >> peer's disk. This is done by calling the fence-peer handler. The handler >> is supposed to reach the >> other node over alternative communication paths and call 'drbdadm >> outdate minor' there." >> >> My question is : if the handler can't reach the other node for any >> reason ,what will happen ? >> > > I always use 'resource-and-stonith', which blocks until the fence action > was a success. As for the fence handler, I always pass the requests up to > the cluster manager. To do this, I use 'rhcs_fence' on Red Hat clusters > (cman + rgmanager) or crm-fence-peer.sh on corosync + pacemaker clusters. > > In either case, the fence action does not try to log into the other node. > Instead, it uses an external device, like IPMI or PDUs, and forces the node > off. > > > B- In active/passive mode , are these directives have effect: >> Are these directives "after-sb-0pri , after-sb-1pri , after-sb-2pri" >> have effects in Active/passive mode or only in Active/Active mode ? >> If they have effects , what if i don't set them , is their default value >> for each ? >> > > It doesn't matter what mode you are in, it matters what happened during > the time that the nodes were split-brained. If both nodes were secondary > during the split-brain, 0pri policy is used. If one node was Primary and > the other remained secondary, 1pri policy is used. If both nodes were > primary, even for a short time, 2pri is used. > > The reason the policy doesn't matter so much is because the roles matter, > not how they got there. For example, if you or someone else assumed the old > primary was dead and manually promoted the secondary, you have a > two-primary split-brain, despite the normal mode of operation. > > > For the previous section , Are you meaning If i assumed the old primary was dead and manually promoted the secondary ,split-brain will happen despite the two nodes can communicate each other ? In other way , would you please explain this : "if you or someone else assumed the old primary was dead and manually promoted the secondary, you have a two-primary split-brain, *despite the normal mode of operation*." , especially underlined sentence ? > > C- can I use SBD fencing with drbd+pacemaker rather than IPMI or PDU? >> > > No, I do not believe so. The reason being that if the nodes split-brain, > both will think they have access to the "SAN" storage. Where as with a real > (external) SAN, it's possible to say "only one node is allowed to talk and > the other is blocked. There is no way for one node to block access to the > other node's local DRBD data. > > IPMI/PDU fencing is certainly the way to go. > > -- > Digimer > Papers and Projects: https://alteeve.ca/w/ > What if the cure for cancer is trapped in the mind of a person without > access to education? > -- KHALED MOHAMMED ATTEYA System Engineer -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20140316/50bdda0e/attachment.htm>