Voice of the DBA

Author: way0utwest

  • Making Guesses

    I was reading a bit about the design and planning stage for a new database that will support some random application. The piece isn’t important, but I did notice one thing. The guidelines are generic, encompassing most of the things we might want to think about: structure of data, constraints, volumes of data and rate of growth, and more. It’s a good list, and one many of you have probably considered at some point if you’ve designed a system.

    However, I’ve rarely been able to actually do more than guess at many of the answers. Even much of the data I can write down is often little more than a guess. Even when I know the DRI constraints, I hesitate to document them separately from the code itself. Mostly because I find designs change early and often, and the documentation is rarely able to keep up with code. The same thing applies with the administrative type decisions I make.

    I’m also nervous about documenting guesses.   I find that far too often any answer I give takes on some level of truth with the developers, often being considered an immutable fact. The assumption that an early guess will match reality later seems to often blind everyone and limits the level to which we can adapt to changing situations.

    As an example, if I tell a SAN admin that we think we need 5GB of space, but we find that we need 20GB in a short period of time, I meet resistance. A debate, or argument ensues, we search for evidence that we need to change, and a very inefficient process ensues. The same thing occurs when developers, security admins, and especially managers hold too tightly to estimates and guesses.

    Certainly some guidelines are needed, but when I’m not sure, I tend to give wide ranges, just to prevent too many expectations from taking hold in people’s minds. We should know that our plans will rarely survive production deployments and workloads, but somehow we forget that when looking at the guesses we make early on.

    Steve Jones

    The Voice of the DBA Podcast

    Listen to the MP3 Audio ( 2.4MB) podcast or subscribe to the feed at iTunes and LibSyn.

  • Deploy from VCS

    Are you confident in your version control practices and code backups? If so, are you willing to do this? Wipe your applications and database schema from your servers and redeploy things from your Version Control System (VCS).

    I’ve typically maintained code in a VCS, but I have to admit I’d be worried about being positive about which version of code was deployed to which server in many of my previous jobs. Only in one position would I have been positive about which code was deployed to every system.

    I was teaching a class recently with Ike Ellis and he mentioned a consultant he knew always asked this. The reason was that if you can’t be confident of the state of your development code, you can’t really have confidence in your refactoring. There will always be places in the code that no one is willing to allow changes, and your flexibility will be limited.

    That’s very true, though even if you know what code you have, I’m sure there will still be sections of your code that no one wants to change. However, our goal should be to get away from code that’s untouchable.

    We should be able to change any code in the system if we have a good reason. When we can make improvements, we should. We need the confidence that we can alter code when we see the need. That means that we need a repeatable, reliable, adaptable software development process. That’s something we can’t build without making the conscious decision to do so.

    Steve Jones

    The Voice of the DBA Podcast

    Listen to the MP3 Audio ( 2.0MB) podcast or subscribe to the feed at iTunes and LibSyn. feed

  • Gauges and Alarms

    I was looking through the news this week and found a piece by Michael J. Swart that I really enjoyed. It talks about different types of metrics that he has used when monitoring and alerting on his database servers. Michaal talks about the difference between alarms and gauges, which are usually base on the time scale in which a DBA or administrator needs to react to a situation. Alarms are created when something grows in a short term and causes an issue. The gauges tend to be longer term items that eventually cause a problem.

    I’ve had a similar view in the past. However I look at these types of metrics from the standpoint of how I tackle my job as a DBA. I also try to think about these issues as a developer, ensuring that telemetry helps track issues that occur over time and acute issues cause a graceful degredation (or exit) and not an unexpected one.

    When I’ve needed to manage systems, I ensure that I have alarms set up. I need these for the situations where something goes wrong in a short period of time. However I never want alarms to be based on a lack of visibility into the system over time. I want to try and eliminate as many alarms as possible with better long term monitoring that looks for indicators that the system might have issues. I’ve found that many (not all) of the alarms that I receive could have been prevented if I’d been paying close attention.

    In other words, I’m a proactive DBA, looking at gauges (using MIchael’s terms), not a reactive one counting on alarms.

    I can’t predict everything, but when I find that looking back at data is helpful. If I find a trend that could have alerted me, I’ll evolve my monitoring system to try and track those potential issues in the future. I’ve written my own custom metrics in the past, which track data, either PerfMon type counters or business data, and then let me know when the growth, decline, or change is unexpected. In this way, I tend to find I can often proactively prevent issues. If I can use my data to “predict” an issue my boss doesn’t believe in, I’ve also found my budget for resources may increase a bit, allowing me to manage systems even better in the future.

    Steve Jones

  • Teambuilding

    I worked in a large company at one point in a team of 20 people. My boss made it a point every month to take a long lunch with the team and engage in some teambuilding. Usually one of us would have to remain at the office, but we rotated the duty so that most of use could participate. We would go to movies, go bowling, have a team lunch, watch a baseball game, or something similar.

    At Redgate, the various groups schedule days out, and last month the company had a large “day out”, bringing many of the Americans over from the US to participate. It was a good time, and the chance to get to know some of people in the company I rarely interact with.

    Team building has been hit or miss, but I’m curious how many of you engage in the activity. I know I’ve worked in plenty of companies where there was no effort made to build a team. This week I wanted to ask you:

    Do you engage in team building at work and what events have you enjoyed?

    Maybe I should ask what worked well to help build a team, but sometimes the enjoyment and bonding go and in hand.

    I thought of this recently as my daughter wanted to ride zip lines for her birthday. We packed up the family to go, and while it wasn’t everyone’s first choice, we enjoyed it and had a few hours to laugh and joke with each other. It turned out to be a much better family bonding time than a few people expected. If you’ve never tried it, I might recommend it as a way to have fun with a small group of people.

    Steve Jones

    The Voice of the DBA Podcast

    Listen to the MP3 Audio ( 2.4MB) podcast or subscribe to the feed at iTunes and LibSyn.