<div dir="ltr"><div>Thank you Digimer very much for your effort & time.<br></div>Would you Please see the question below ? :)<br><div><div><div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Mar 14, 2014 at 4:44 PM, Digimer <span dir="ltr"><<a href="mailto:lists@alteeve.ca" target="_blank">lists@alteeve.ca</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="">On 14/03/14 05:34 AM, khaled atteya wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
A- In DRBD Users's guide , in explanation of "resource-only" which one<br>
of fencing policy , they said:<br>
<br>
"If a node becomes a disconnected primary, it tries to fence the<br>
peer's disk. This is done by calling the fence-peer handler. The handler<br>
is supposed to reach the<br>
other node over alternative communication paths and call 'drbdadm<br>
outdate minor' there."<br>
<br>
My question is : if the handler can't reach the other node for any<br>
reason ,what will happen ?<br>
</blockquote>
<br></div>
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.<br>
<br>
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.<div class=""><br>
<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
B- In active/passive mode , are these directives have effect:<br>
Are these directives "after-sb-0pri , after-sb-1pri , after-sb-2pri"<br>
have effects in Active/passive mode or only in Active/Active mode ?<br>
If they have effects , what if i don't set them , is their default value<br>
for each ?<br>
</blockquote>
<br></div>
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.<br>
<br>
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.<div>
<br><br></div></blockquote><div>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, <u>despite the
normal mode of operation</u>." , especially underlined sentence ? <br></div><div><br> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div class="">
<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
C- can I use SBD fencing with drbd+pacemaker rather than IPMI or PDU?<br>
</blockquote>
<br></div>
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.<br>
<br>
IPMI/PDU fencing is certainly the way to go.<span class=""><font color="#888888"><br>
<br>
-- <br>
Digimer<br>
Papers and Projects: <a href="https://alteeve.ca/w/" target="_blank">https://alteeve.ca/w/</a><br>
What if the cure for cancer is trapped in the mind of a person without access to education?<br>
</font></span></blockquote></div><br><br clear="all"><br>-- <br><div dir="ltr"><div style="text-align:center"><div style="text-align:left">KHALED MOHAMMED ATTEYA</div><div style="text-align:left">System Engineer</div><div style="text-align:left">
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