Databases on VMware?
Running databases in a VMware environment has been successful at many companies. If you are faced with a database virtualization project, and especially if past projects have failed, ensure the correct monitoring metrics are being used in troubleshooting scenarios. If only O/S metrics are being relied on, these may be wrong and cause the DBA team and others to make incorrect assumptions and decisions. VMware’s vCenter is not aware of databases, and databases don’t know they’ve been virtualized
Obtaining access to vSphere and/or installing DPA with VM option from SolarWinds is a key step to getting a complete picture of performance at the VM, but also the physical host, storage and networks layers too. Monitoring the correct metrics that can help show where the bottlenecks are.
VMware changed the rules about what server resources were required to keep a database responding predictably, making it much more difficult for DBAs to see the interaction between the database and the underlying server resources. Predictable performance and availability of databases are critical to supporting the entire application stack.
Trouble Spots with Databases on VMware
1) Inaccurate metrics – database server metrics on virtual servers are inaccurate
2) Dynamic Resource Allocation – shifting resources impact database performance
3) No Control over Host Resources– other VMs on the host server affect resource allocation
4) Limited DBA Visibility – DBAs typically don’t have access to vCenter
5) Mutual Ignorance – vCenter is not aware of databases, and databases don’t know they’ve been virtualized
1) Inaccurate metrics – database server metrics on virtual servers are inaccurate
Using traditional database monitoring and performance tools, the status of server health metrics such as CPU, memory, and storage are inaccurate on a VMware hosted servers. For example, if a virtual machine is allocated 8GB of RAM, but has a 4 GB memory limit, what is the memory utilization for that O/S if it’s currently using 3.8GB? The O/S will report the memory utilization as 3.8 / 8 or 47.5%. However, since there is a VM limit in place, the real utilization is 3.8 / 4 or 95%. The distinction has a huge impact on database performance. This is one potential problem you will encounter if you use O/S metrics for monitoring performance and availability.
2) Dynamic Resource Allocation – shifting resources impact database performance
VMware dynamically moves resources between VMs and moves VMs between different physical host servers. “VMware vMotion technology leverages the complete virtualization of servers, storage and networking to move an entire running virtual machine instantaneously from one server to another.1” What does the DBA see when a CPU is removed, memory is re-allocated, or the virtual server changes to a new host? Nothing. A virtue of VMware is complete transparency for the application. But when the application is a resource sensitive database, and the DBA team has years of experience optimizing their instances to match available resources, hiding the underlying resources leaves the DBA unable to perform their tasks and maintain performance levels. Without visibility to dynamic VM changes, the DBA and the database are vulnerable.
3) No Control over Host Resources– other VMs on the host server affect resource allocation
When hosting databases on a physical server, changes occurring elsewhere do not affect the database server. On a virtual platform, however, changes to allocated resources or new application loads on other virtual machines sharing the same host server can significantly affect the response of a VM.` Without awareness of the other VMs and the systems they host, the DBA cannot understand the causes or accurately respond to stresses on their own VM.
4) Limited DBA Visibility – DBAs typically don’t have access to vCenter
VMware Administrators use VMware vCenter, but because of security concerns and the expertise required, they severely restrict access to vCenter. (This is no different than DBAs controlling access and privileges in their database environment.) In surveys of organizational cooperation between different IT infrastructure groups, fewer than 20% of DBAs reported having even limited visibility or experience with vCenter and monitoring of VMware status. As a result, the DBAs responsible for database performance and availability on VMware have no visibility to virtual server or host status, changes, and resources. No tools or infrastructure typically exist to promote sharing of the most basic system status and change notifications. While the Director of IT may want cross departmental cooperation, typical tools are designed to prevent it.
5) Mutual Ignorance – vCenter is not aware of databases, and databases don’t know they’ve been virtualized
DBAs have specialized tools and scripts for database monitoring, but these tools they are not aware that the server is virtual, not physical. These tools, scripts and processes were all built for a physical environment. And according to VMware, “…an operating system or application cannot tell the difference between a virtual machine and a physical machine”2. And as explained above, the VMware administration group cannot share their views and tools with the DBA counterparts. How can a DBA team be held responsible for high availability systems without having accurate visibility to the servers they are hosted on?
SUMMARY
Visibility Reduces Risk
70% of application performance problems occur at the database level. And because databases have such stringent performance requirements and are so sensitive to configuration changes, databases are the most recent converts to VMware. Recommended configurations from VMware for Oracle, for example, list multiple changes to database configuration and VMware settings required to optimize availability. Moving databases without making them virtualization aware puts the entire VMware initiative at risk. Be prepared to make the move. Give the DBA team the visibility needed to ensure their success on the virtual servers.
Databases on VMware – our Solution:
Database Performance Analyzer (DPA) from SolarWinds provides the fastest way to identify and resolve database performance issues. DPA is part of the SolarWinds family of powerful and affordable IT solutions that eliminate the complexity in IT management software. DPA’s unique Multi-dimensional Database Performance Analysis enables you to quickly get to the root of database
problems that impact application performance with continuous monitoring of databases on physical, Cloud-based and VMware servers.
Database Performance Analyzer Customer Success Center
DPA Starts at € 1.715 + DPA VM Option Starts at € 735
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