On Tue, Jul 11, 2017 at 7:17 AM, TranceWorldLogic . < tranceworldlo...@gmail.com> wrote:
> Hi, > > 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. > > I have also modified vdsm.com to allow 2 replica count. > > But latter I found in code it is hard coded to 3 as shown below: > ------------------- ------------------------------- > ------------------------------ --------------- > src/plugins/gr-he-setup/storage/nfs.py > > if* replicaCount != '3'*: > raise RuntimeError( > _( > 'GlusterFS Volume is not using replica 3' > ) > ) > ------------------- ------------------------------- > ------------------------------ --------------- > > Can I get to know the reason to hard coded to 3 ? > 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 ?) > Simply because two is even and three is odd. 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. With three nodes, if node says A but nodes B AND nodes C says B, the truth is B by design. That's why you need three nodes with at least 2 of them up and working. If you want to save something on storage side you could evaluate two regular nodes plus an arbiter one. > > If I am missing something please let me know. > Also want to understand, can quorum can solve 2 node gluster issue > (split-brain) ? > > Thanks, > ~Rohit > > > _______________________________________________ > Users mailing list > Users@ovirt.org > http://lists.ovirt.org/mailman/listinfo/users > >
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