Voice of the DBA

Author: way0utwest

  • Resource Governer–Memory Limits

    I had looked at the Resource Governor early on when it was being developed and first released on SQL Server 2008, but I hadn’t spent a lot of time on it. It was the first cut at a throttle that I had been asking for since 2001 or 2002 when I saw IIS get a CPU throttle. I loved the idea of being able to slow down the amount of CPU that an individual query could take, which I thought would really help limit the amount of damage that a particular query could do on your system.

    However I hadn’t spent much time on the memory limits. While studying for the MCM, I downloaded this white paper and watched the Paul Randal video from Technet. In it, I was reminded that the memory limits you set apply to the query memory, not the buffer pool memory.

    What does this mean? It means that while you can limit the memory that a query uses for it’s data, for it’s plans, etc., you can’t prevent a query from flushing the buffer pool when it causes a lot of reads from disk.

    This is a limitation of the Resource Governor, and we might see this changed later, but it’s a good thing to remember that you cannot use Resource Governor as a way to guarentee predictable performance from your SQL Server. The engine is still a shared resource and one person can still affect it’s operation. Resource Governor does allow you to limit the damage, and it can be used to prevent someone from bringing the instance to a standstill. However it does not provide the complete control that you might assume is implied from the name.

  • The Importance of My Cloud Data

    I recently rebuilt my laptop, and when I installed Office, there was an offer to sync my Office data up to the cloud. I declined since I already use Live Mesh to sync data across multiple machines, a Windows Home Server for local backups, and Dropbox for remote ones. It’s not that I don’t like the cloud, but that I’m not sure I, Steve Jones, can trust the cloud.

    There was an outage at Hotmail recently that involved SQL Server. That’s bound to happen as the larger you are, the more likely it is that you will have some sort of failure.  It’s inevitable, and hopefully you have done enough planning to recover quickly. I don’t know where the Hotmail team failed, but they certainly failed somewhere.

    The cloud works because it provides some great economies of scale, a much more efficient use of computing resources. For many people, that means it can also be a much cheaper way to get the services they need. Even companies could do find advantages in using cloud-based services.

    However this outage shows one of my major concerns. It’s not that I find Hotmail unreliable, or that I worry about security. It’s that when something breaks, and it will, I’m not sure Hotmail will care a lot about my data. If Steve Jones, Inc., a company paying Microsoft $1000 a year for mail, Office, etc.,  winds up losing 3 days of service and 1 week’s worth of data, will Microsoft care? What if the same failures affect a large company, one that pays Microsoft $1,000,000 a year? Whose data will they work harder to restore?

    Ultimately economics and realities set in. Microsoft, and every single other cloud provider out there, will worry about the larger customers first, and perhaps not even bother to finish restoring data for the smallest ones if there is not enough cost benefits. They might even refund the payments of someone to compensate them.

    If it’s my data, however, I’m not sure that’s good enough. I’m also not sure it’s a risk I want to take.

    Steve Jones

    (originally published at http://www.sqlservercentral.com/articles/Editorial/72146/)

    Podcasts

  • CTRL Scroll and Getting Old

    The handiest thing that I’ve used lately for a computer is the Ctrl button and the scroll wheel on my mouse. If you’ve never tried it, do it now on this web page. Scroll different directions and you’ll see what I mean.

    Here’s the default view of my blog:

    scroll1

    It’s not bad, and from about 2, 2.5 ft away, I can read this. However if I CTRL and scroll up a couple clicks, I get this:

    scroll2

    Not a huge difference in the images, but much easier to read.

    As I get older it gets harder to read images on the screen, especially when I’m trying to get a lot done. It’s easy to scroll down, but I was finding myself scooting forward on my chair and leaning in. Not the best ergonomics. So I sat back (in my new chair), and made all my fonts bigger. I upped the default sizes in Word, OneNote, EditPlus, etc.

    Getting old is hard, but technology makes this easier. I even run a larger font in my Kindle apps than I Delaney because it’s just easier to read.

    And more fun than browsing the limited supply of large print books at the library.

  • NoSQL Basics

    Last year there was quite a bit of press devoted to the NOSQL movement, emphasizing the scalability and power of this class of databases. They have not been well known, but have been used to power some of the very well known Internet companies out there. Companies like Google, Facebook, and others are using NoSQL databases in places, achieving the scalability that many RDBMS’s have struggled to achieve without enormous costs.

    I ran across an article that talks about some of the basics of what is classified as a NOSQL database. It’s written more for managers, and it does a good job of warning them that NOSQL is not the “answer” to all your performance problems. It’s a piece of technology that fits in some places and in some situations.

    Should you care about NOSQL? I think you should, if for no other reason than some manager will ask you about it at some point. Or a developer will want to build an application using a NOSQL database. A flat “no” from the data group is counter-productive,  and is not appropriate. If you are going to rationally argue against a new technology, you should have some basic understanding of how it works, what problems it solves, and engage in a logical debate.

    There are lots of good NOSQL articles out there, and perhaps the first thing you should learn is that there are different types of technologies for solving different problems. Cassandra is not interchangeable with MongoDB, and Voldemort is different from the other two. None of them is a direct replacement for SQL Server (or another RDBMS), but they do work in different areas. If you’ve never seen the CAP triangle, take a look at it now.

    Many of you are data professionals, and SQL Server specialists, and that’s fine. That doesn’t mean you shouldn’t learn a little something about other technologies, and how they might compare and contrast with SQL Server. Here’s a nice basic article from SQL Server Master to get you started.

    Steve Jones

    (originally published at http://www.sqlservercentral.com/articles/Editorial/72127/)

    Podcasts: