Running a database on EC2? Your clock could be slowing you down

Why would you run your own Postgres instance on EC2 within AWS? That kind of defeats the purpose of paying for AWS. Why not use Postgres RDS or Aurora?<p>It makes some sense with Sql Server and Oracle in a few cases because of licensing but hosting your own Postgres instance on AWS is the worse of both worlds -- you&#x27;re paying more than with a cheaper VPS and you have to do all of the maintenance yourself and not taking advantage of all of things that AWS provides -- point in time restores, easy cross region read replicas, faster disk io (Aurora), etc.

This is exactly why I wrote the &quot;clockperf&quot; tool during the time I was working at AWS: <a href="https:&#x2F;&#x2F;github.com&#x2F;tycho&#x2F;clockperf" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;tycho&#x2F;clockperf</a><p>At the time, we were trying to benchmark disk I&#x2F;O for new platforms, but we found that things were underperforming compared to the specifications for the hardware. We figured out that fio was reading the clock before&#x2F;after each I&#x2F;O (which isn&#x27;t really necessary unless you really care about latency measurement) and just by reading the clock we were rate limiting our I&#x2F;O throughput. By switching to &quot;clocksource=tsc&quot; in our fio config, we managed to get the performance behavior we expected.

Nice article!<p>If you&#x27;re interested in clocks on Linux, you might also find this article useful (shameless plug): <a href="http:&#x2F;&#x2F;btorpey.github.io&#x2F;blog&#x2F;2014&#x2F;02&#x2F;18&#x2F;clock-sources-in-linux&#x2F;" rel="nofollow">http:&#x2F;&#x2F;btorpey.github.io&#x2F;blog&#x2F;2014&#x2F;02&#x2F;18&#x2F;clock-sources-in-li...</a>

here is a link that doesnt have the ssl problem: <a href="http:&#x2F;&#x2F;archive.is&#x2F;7zVmu#selection-1533.0-1536.0" rel="nofollow">http:&#x2F;&#x2F;archive.is&#x2F;7zVmu#selection-1533.0-1536.0</a>

an older discussion of this: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=13813079" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=13813079</a>

<i>And, EC2 does not live migrate VMs across physical hosts. I couldn’t find anything explicit from AWS on this, but it’s something that Google is happy to point out.</i><p>Is it a good idea for a production database to depend on a feature not being used when the vendor hasn&#x27;t said that they don&#x27;t or won&#x27;t use it? They may very well live-migrate when convenient, but just don&#x27;t expose that functionality to customers since they don&#x27;t want customers demanding it.

Is AWS NVMe still ephemeral and how do you deal with it? What happens if a machine, or several, reboots?

We set our server 4 hours ahead!