<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jul 11, 2017 at 7:17 AM, TranceWorldLogic . <span dir="ltr"><<a href="mailto:tranceworldlogic@gmail.com" target="_blank">tranceworldlogic@gmail.com</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 dir="ltr"><div><div><div><div><div>Hi,<br><br></div>I was trying to setup hosted engine on 2 host machine but it not allowing to setup hosted engine on 2 node gluster file system.<br><br></div>I have also modified <a href="http://vdsm.com" target="_blank">vdsm.com</a> to allow 2 replica count.<br><br></div>But latter I found in code it is hard coded to 3 as shown below:<br>------------------- ------------------------------<wbr>- ------------------------------ ---------------<br>src/plugins/gr-he-setup/<wbr>storage/nfs.py<br><br> if<b> replicaCount != '3'</b>:<br> raise RuntimeError(<br> _(<br> 'GlusterFS Volume is not using replica 3'<br> )<br> )<br>------------------- ------------------------------<wbr>- ------------------------------ ---------------<br><br></div>Can I get to know the reason to hard coded to 3 ?<br>from online I got to know that split brain issue not get resolve automatically using 2 node gluster setup. But please let me know more (why 3 ? why not 2 or 4 ?)<br></div></div></blockquote><div><br></div>Simply because two is even and three is odd.<br><br>In a split condition over only two nodes, if node A says A and nodes B says B you cannot decide if the truth is A or B.</div><div class="gmail_quote">With three nodes, if node says A but nodes B AND nodes C says B, the truth is B by design.<br></div><div class="gmail_quote">That's why you need three nodes with at least 2 of them up and working.<br><div><br></div><div>If you want to save something on storage side you could evaluate two regular nodes plus an arbiter one. </div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><br></div><div>If I am missing something please let me know.<br></div><div></div><div>Also want to understand, can quorum can solve 2 node gluster issue (split-brain) ?</div><div><br>Thanks,<br></div><div>~Rohit<br></div><div><br></div></div>
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