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  • Geek City: What Triggered This Post?

    I’d really like to get another post up onto my much neglected blog before the end of 2012. This will also start one of my New Year’s resolutions, which is to write at least one blog post a month. I’m going to tell you about a change in SQL Server that wasn’t announced in any “What’s New” list that I ever saw, perhaps because it was just a chance ...
    Posted to Kalen Delaney (Weblog) by Kalen Delaney on December 31, 2012
  • CloudSeeder: CLR Stored Procedures For Creating CPU Pressure

    Sometimes, in the interest of testing various scenarios that your server might encounter, it's useful to be able to quickly simulate some condition or another. I/O, memory, CPU pressure, and so on. This latter one is something I've been playing with a lot recently. CPU pressure in SQL Server creates all sorts of interesting side-effects, such as ...
    Posted to Adam Machanic (Weblog) by Adam Machanic on October 23, 2012
  • Performance impact: driving up context switches/sec

    Too many context switches per second are considered bad for your database performance. But how many is too many has never been clear. With the core count of new servers going up rapidly, it becomes even less clear how we should evaluate this counter to help understand the SQL Server behavior in the environments we support. Recognizing that any ...
    Posted to Linchi Shea (Weblog) by Linchi Shea on January 12, 2012
  • Performance impact: hyperthreading for OLTP queries -- II

    This is in part a response to a comment by Paul White (@SQL_Kiwi) to my previous post on the performance impact of enabling hyperthreading (HT) on OLTP queries, and in part due to my desire to capture a more complete set of test data for future investigation on this very topic. I’m posting below the results of re-running the same exact test as ...
    Posted to Linchi Shea (Weblog) by Linchi Shea on January 11, 2012
  • Performance impact: hyperthreading for OLTP queries

    My previous post focuses on the performance impact of enabling hyperthreading (HT) on a machine with four Intel Westmere-EX processors on reporting queries. Let’s turn our attention to OLTP queries. To oversimplify it, reporting queries are generally processed by scanning a large number of pages, whereas quick index seeks are the hallmark of OLTP ...
    Posted to Linchi Shea (Weblog) by Linchi Shea on January 5, 2012
  • How Microsoft helps you NOT break your Windows Azure Application: Storage Services Versioning

    One of the advantages of using Windows Azure to run your code is that you don’t have to constantly manage upgrades on your platform. While that’s a big advantage indeed, it immediately brings up the question - how do the upgrades happen? Microsoft upgrades the Azure platform in periodic increments, and the components that are affected are ...
    Posted to Buck Woody (Weblog) by BuckWoody on December 6, 2011
  • Why generalizations are dangerous

    A couple of years ago, John Sansom wrote a blog post comparing the performance of two different ways to get the maximum value from a column: MAX() and TOP (1). http://www.johnsansom.com/performance-comparison-of-select-top-1-verses-max/ In the conclusion, he states:  When a clustered index is present on the table & ...
    Posted to Aaron Bertrand (Weblog) by AaronBertrand on September 15, 2011
  • Plan for Diagnostics in Cloud Computing From the Git-Go

    “Git-Go” is something we say in the South that means “right at the start”. I’ve seen several applications for on-premise systems that don’t have much in the way of diagnostics - the developers rely on a debugger, the event logs on the server and client workstation, and most of all, the ability to watch the system from end-to-end. This approach ...
    Posted to Buck Woody (Weblog) by BuckWoody on September 6, 2011
  • Performance impact: The cost of doing small lookups in a large batch update

    Lookup tables are widely used in database applications for good reasons. Usually, a lookup table has a small number of rows and looking it up with a join is fast, especially when the table is already cached. Recently, I needed to update every row in many relatively large tables, each of which was identically structured, had ~25 million ...
    Posted to Linchi Shea (Weblog) by Linchi Shea on April 4, 2011
  • Linked servers: how long do they stay connected?

    I was looking at some of my old notes on linked servers and found a tidbit on how the linked server connections are managed by SQL Server. I'm posting it here because I don’t think the information is widely known. When you make a linked server call from a SQL Server instance (say ServerA) to another SQL Server instance (say ServerB) over ...
    Posted to Linchi Shea (Weblog) by Linchi Shea on March 31, 2011
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