title: How does Amazon RDS backup/snapshot actually work?
body: <p>I am an Amazon RDS customer and am experiencing daily amazon RDS write latency spikes, corresponding roughly to the backup window. I will also see spikes at the end of a snapshot (case in point: running a snapshot takes appx 1 hour, and in the final 5 minutes, write latency spikes). I am running a multi-AZ m1.large deployment. </p>
  
  <p>Is there anyone on Stack who can explain how Amazon RDS backup is <em>actually</em> working?  I've read the Amazon RDS docs, and as far as I can tell, Amazon RDS is not behaving according to spec. Specifically, these backup/snapshot operations should be hitting my replica, and therefore not causing any downtime/performance hit, or so I thought. </p>
  
  <p>I can distill my problem into six questions:</p>
  
  <ul>
  <li>What is technically happening during a snapshot and a backup, and how are they different? (If you answer this question, please tell me if you are able to empirically confirm your answer, or are simply quoting me documentation).</li>
  <li>Is a spike in write latency to be expected during the backup window on a multi-AZ deployment?</li>
  <li>Is a spike in write latency to be expected at the end of a snapshot on a multi-AZ deployment?</li>
  <li>Would my write latency spike be even higher if I was not multi-AZ ?</li>
  <li>Architecturally, would I be able to avoid these write latency spikes if I rolled my own database running on two m1.large EC2 instances? </li>
  <li>Are there any configurations I can use that would avoid these write latency spikes while still hosting my DB with RDS, or am I effectively at the mercy of Amazon? </li>
  </ul>
  
  <p>Bonus Question: where and how do you host your mysql database?</p>
  
  <p>I can say that I have been generally happy with RDS except for these daily write latency issues. I love the built-in database monitoring and it was fairly simple to setup and get going. </p>
  
  <p>Thanks!</p>
  
  <p><img src="https://i.stack.imgur.com/YgyYB.png" alt="amazon RDS write latency"></p>