title: Why Hbase need WAL？
body: <p>I'm new to Hbase, and I found that Hbase will write all the operations to WAL and memstore. </p>
  
  <blockquote>
    <p>Q1: I wonder why Hbase need WAL? </p>
    
    <p>Q2 : Hbase must write to WAL every time when I put or delete data, why
    don't operate it just in its data file?</p>
  </blockquote>