<p>I made a OKD 4.9 cluster.</p>
<p>I successfully installed openshift and made a cluster, but I got a question now.</p>
<p>There is a sentence in OKD document.</p>
<p>&quot;The only supported values is 3, which is the default value&quot;</p>
<p>I think there is an important reason to do not use 5, 7 masters.</p>
<p>Could you guys tell me why?</p>

jonghyun Kim
<blockquote>
<p>I think there is an important reason to do not use 5, 7 masters.</p>
<p>Could you guys tell me why?</p>
</blockquote>
<p>Technically it is still possible to have 5 or 7 Master Nodes, there is nothing in place to stop you. It is just not supported, so if you have a problem with it you'll have to deal with it yourself.</p>
<p>However, you should understand why this recommendation is there. Many Kubernetes Master components (<strong>Controller Manager</strong>, <strong>Scheduler</strong>) are only active on one single Master Node anyway, while the same component on all other Masters are not active. <strong>API Server</strong> is active-active, so API Server scales nicely.</p>
<p>For <strong>etcd</strong>, Raft is leader-based; the leader handles all client requests which need cluster consensus. Any request that requires consensus sent to a follower is automatically forwarded to the leader. So for write operations or for consistent reads, there is an overhead if you have more than 3 etcd members. If you have more etcd members, this overhead gets larger, but YMMV.</p>
<p>So it comes down to additional <em>overhead</em> with 5 or 7 Master Nodes.</p>
