Understanding Database Impact on Storage
One of the challenges with understanding storage in a virtualized environment, is the specific use-case around database systems. In fact, there are multiple use-cases within the various types of database environments that can each have very distinct performance characteristics.
Exactly the same, but a little different
Have you ever heard the classic phrase from someone who says “it’s exactly the same, but a little different” which would imply it is a simple A/B comparison that should have nearly no differences. When it comes to different database applications, including OLAP, OLTP, Analytics, and Reporting databases, there are significant differences in the performance profile.
Quite often, virtualization administrators move workloads around into different storage environments for a variety of reasons which are often led by space issues. Secondary to storage space, performance is the often the second place in the priority which leads us to a common issue. Database server performance is not just a matter of it being a database server which confuses the issue.
As you can see from the chart in the image above, there are some distinct differences with how the different type of database applications draw on storage resources. Frank Denneman of PernixData had done a great post which explains what the chart is about, and how database virtualization is changing the way that storage is being architected.
Using this, and the additional posts that are linked at the bottom of the article, you can help guide yourself to better strategies for designing storage infrastructure.
Don’t Blame the SAN. Blame the SAN Design
As data center administrators, we have many jokes about where to point the blame when a performance issue arises. The top 2 issues that will come up are typically the storage, and the network.
As database administrators launch into troubleshooting mode during performance challenges, it will be well received if we take the time to evaluate what the database engine is doing, and what the storage configuration is.