title: Why NoSQL is better at "scaling out" than RDBMS?
body: <p>I have read the following text in a <a href="http://tekedia.com/12083/nosql-database-advantages-and-disadvantages/" rel="noreferrer">technical blog</a> discussing the advantages and disadvantages of NoSQL:</p>
  <blockquote>
  <p>&quot;For years, in order to improve performance on database servers, database administrators have had to buy bigger servers as the database
  load increases (scaling up) instead of distributing the database
  across multiple “hosts” as the load increases (scaling out). RDBMS do
  not typically scale out easily, but the newer NoSQL databases are
  actually designed to expand easily to take advantage of new nodes and
  are usually designed with low-cost commodity hardware in mind.&quot;</p>
  </blockquote>
  <p>I became confused about the scalability of RDBMS and NoSQL.</p>
  <p>My confusion are:</p>
  <ol>
  <li>Why RDBMS are less able to scale out? And the reason of buying bigger servers instead of buying more cheap ones.</li>
  <li>Why NoSQL is more able to scale out?</li>
  </ol>