VMs are not VMs

I was at VMWare recently. One of the main things that all of the SQL Server professionals that were there tried to emphasize is that SQL Server workloads are not like other workloads. The impact on the various host resources, the stress on the storage systems, these are fundamentally different in a database server. The loads tend to be higher, but not always, however the tolerance for delays tends to be lower than for many other types of applications.

This becomes an issue if you work in an organization that doesn’t understand the challenges of database systems. It’s entirely possible that your virtualization administators, or your storage administrators don’t recognize that the SQL Server might need more resources. Or they don’t believe the impact is greater for the organization. To be fair, that might be true, but someone other than the DBA or system administrator should decide if the database is more important than the file server and should be treated differently from an infrastructure perspective.

No matter what level of resources your database server need, it’s not going to run like other systems. Typically this means that the density of VMs has to change when a database server is involved. As an example, I know of a system that typically has a 10:1 guest:host ratio for most of their server systems. However for SQL Servers it’s 4:1 or lower. The same is true for storage. Aggregate bandwidth doesn’t always reflect the ability of a storage system to keep up with database requests. It becomes important that both you and your storage administrators learn to speak the same language and understand what requirements exist for SQL Server VMs.

Virtualization really starts to highlight the advantages of a DevOps environment. DBAs and developers should work closely with the virtualization and storage administrators to learn what each others’ requirements are and how each of us can help the other perform their particular job at a higher level. Infrastructure staff can help prepare standard environments and ensure production looks like staging. Developers and DBAs can help a vSphere admin learn a little PowerCLI and programming. That might get them to be more cognizant of the particular requirements of your SQL Server and be more willing to work with you.

Steve Jones

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