SQL SERVER – Overall SQL Server Performance – Not Just Query Performance – Notes from the Field #008

[Note from Pinal]: This is a new episode of Notes from the Field series. When SQL Server is slow we think we can improve the performance of the server by just increasing the performance of queries. However, sometimes the queries are already doing good and there is no increase in the speed even though we tune the queries. It is very crucial to know where exactly the problem is with the system as well understand how to improve the performance of overall system. In this blog post David has very interesting approach where he explained how one can systematically work with system and improve the performance of overall server.

In this episode of the Notes from the Field series database expert David Klee explains a very crucial issue DBAs and Developer faces in their career – how you can improve performance of overall server. Linchpin People are database coaches and wellness experts for a data driven world. Read the experience of David in his own words.


Too many times I see DBAs fighting to squeeze out performance from a poor performing SQL Server database. Hit your favorite search engine and look for SQL Server performance and the majority of the results are talking about query tuning, execution plans, and index techniques. Occasionally, problems do exist outside of the database! I wholeheartedly agree that these topics are vitally important for any DBA to become proficient at, but it should not be the only layer of focus when performing tuning. Instead, step back a bit and approach the problem holistically and at least spot-check the health of the various layers around your databases.

My analogy is simple. You are driving down the road and your car suddenly slows to a crawl. Taking the ‘start at the query’ approach is akin to immediately opening the engine bay and looking at the motor. The holistic approach is to first walk around the car and look for anomalies en route to the hood, where you might discover that you have a problem like a flat tire.

As a DBA, you do not have to be masters of each layer of the infrastructure stack. However, having a conceptual understanding of how each of these layers and their impact to your SQL Servers will help you triage performance concerns quicker and more reliably. Just look at the individual components in this hypothetical infrastructure around your application!

Now, I am in no way advocating always throwing more hardware at any performance problem. That action always leads to bigger and more expense problems down the road. I want you to help the business get the most out of the infrastructure that they already own and manage.

Storage is the largest source of issues that I routinely encounter. Three main issues constantly pop up, all of which have a tremendous (and silent) impact on SQL Server’s performance: throughput, operations per second, and latency. The root causes of any of these issues vary widely, but all can be at least identified and measured with SQL Server metrics such as sys.dm_io_virtual_file_stats, and wonderful tools such as SQLIO  and IOMeter. These tools can be used to establish your storage performance characteristics at all workload levels, and then Windows Perfmon or other third-party tools can be used to track your steady-state storage utilization.

Virtualization can cause silent performance hits when it is designed for consolidation and not the performance of resource-hungry business-critical applications such as SQL Server. Key architectural items such as CPU overcommitment and VM specifications can be overlooked and cause wildly variable performance characteristics, none of which are good for your databases.

Even a topic as subtle as networking can be a huge performance drain. Ever notice the SQL Server wait statistic ASYNC_NETWORK_IO? It means that either your application cannot consume the data fast enough that SQL Server is sending it, or that a network problem is slowing down the transmission of the data. A utility such as iperf can help you test your end-to-end network performance  and help identify network issues.

No matter the tools or techniques used in the daily tradeoffs for performance, the key to understanding the impact of these problems is to establish a system performance baseline when everything is known to be working well. By establishing a baseline, and then periodically updating the baseline with the latest repeatable system benchmarks, you know if your systems are performing at their peak capability or if something is unhealthy. Quick metrics that benchmark the entire instance, such as DVDstore , can be used to quickly check the relative performance of an instance compared to its known optimal value.

Establish your baselines of each portion of the system stack that you have some level of dependency on. Understand the additional layers that indirectly impact your database performance. Put it all together and scrutinize each piece and you can help squeeze the most performance out of your existing infrastructure!

If you want to get started with performance analytics and triage of virtualized SQL Servers with the help of experts, read more over at Fix Your SQL Server.

Reference: Pinal Dave (http://blog.sqlauthority.com)

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2 thoughts on “SQL SERVER – Overall SQL Server Performance – Not Just Query Performance – Notes from the Field #008

  1. Pingback: SQL SERVER – Roundup Post – Notes from the Field – Year 2013 – Performance Tuning and Database Health | Journey to SQL Authority with Pinal Dave

  2. Pingback: SQL SERVER – Contest Post – Notes from the Field – Learning Performance Tuning and Database Health | Journey to SQL Authority with Pinal Dave

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