I was working with the customer today investigating MySQL over DRBD performance issues. His basic question was why there is so much overhead with DRBD in my case, while it is said there should be no more than 30% overhead when DRBD is used.

The truth is - because how DRBD works it does not adds static overhead which could be told as 10% or 80% and you really need to understand how DRBD works as well as how IO system is utilized to understand how much overhead you should expect.

First lets talk what kind of IO you performance you care about while running MySQL over DRBD. Your reads are going to be serviced from local hard drive and it is only writes which suffer overhead of DRBD.
If you're using MySQL with Innodb (and running MyISAM with DRBD makes little sense anyway) you will have to care about background random IO coming from buffer flush activity - which is typically not latency critical and rarely the problem and log …

This week I had to face one but very weird problem. Each and every time I tried to compile and build MySQL server on Ubuntu 7.10 from source files the process ended up with errors. Most commonly it was Segmentation fault error but sometimes the OS just stopped responding (something like BSOD on Windows).

I followed the instructions on MySQL Installation Using a Source Distribution. The tools I use are newer than suggested there so I doubt they cause such an error. Also i tried to ./configure with different keys as suggested but with no luck. Now below you will see that the error occurs while compiling different sources. My concern is that the issue is with OS or my hardware. I was running memtest86 for a couple of hours and it says the RAM is ok. So after dozen of times doing cleaning and building I'm really close to give up …

Over the last few years there has been a lot of fanfare around open source companies and their liquidation events. Most of the news has been around Sun’s billion dollar acquisition of MySQL or the Citrix acquisition of Xen and even Yahoo’s acquisition of Zimbra. In contrast there was little attention paid to the SourceFire. Actually if you ask most open source users about SourceFire they would probably answer “SourceWho?” If you ask open source users if they have heard of ClamAV or Snort they probably would be able to tell you that they are the leading open source software for virus protection and intrusion detection respectively. Recently, SourceFire has been in the news a …

SimpleXML is neat.  Some people don't think it is so simple.  Boy, use the old stuff.  The DOM-XML stuff.

Anyhow, one annoying thing about SimpleXML has to do with caching.  When using web services, we often cache the contents we get back.  We were having a problem where we would get an error about a SimpleXML node not existing.  We were caching the data in memcached which serializes the variable.  So, when it unserialized the variable, there were references in there to some SimpleXML nodes that we did not take care of.  Basically, a tag like:

<foo>bar</foo>

is a string.  But a tag like:

<foo></foo>

is an empty SimpleXML …

Ever wish you could have a browser based shell for Google? One that was clutter and advertising free? Say hello to Goosh, one of the coolest service to hit the web.



It even recognizes 'clear' :) For now, I am addicted to it.

KEY ACCOMPLISHMENTS LAST WEEK

• I integrated some changes from the past semester into the Skoll Client source code. These changes will allow the client to collect more detailed information of the testing process. One of such change is creating a separate log file for each step of the testing process.
• I created a mock-up for the new HTML testing report pages. The goal of the new report pages is to combine the interfaces of push-build and Skoll. Push-build provides very detailed information of testing process, while Skoll is good at visualizing huge number of test results. The new interface looks promising, but lots of improvements will be added later on.
• I began to modify the module that's responsible for generating the HTML testing report pages. This week I separated test result generation from HTML generation, so in the future other reporting interfaces can be implemented for the test results. Eventually, the …

In recent years, the software tools business has been a tough one. While Borland was a high flyer in the 80s and early 90s, the tools business was commoditized by and large by Eclipse over the past few years. The company is a shadow of its former self and recently sold off its development tools business to Embarcadero. But Borland isn't the only casualty in the tools space. There's been ongoing consolidation in tools for years. And we've seen other tools companies suffer, too. Agitar, which by all accounts had impressive testing tools and a great pedigree, recently decided to... READ MORE

KEY ACCOMPLISHMENTS LAST WEEK

• Even though this is the start of the SoC, I have been working on MySQL testing for some time now. My research group at University of Maryland has been working on automated testing for highly configurable software, and we have been testing MySQL for awhile. Our project is called Skoll (http://www.cs.umd.edu/projects/skoll/contribute/mysql.html), which automatically tests highly configurable software on distributed computing resources.

KEY TASKS THAT STALLED LAST WEEK

• Finished all my final exams and projects last week, ready to start this project full time.

KEY CONCERNS

• I contacted MySQL to get access to push-build source tar balls, so Skoll can test each "push release" of MySQL instead of each check-in. I am waiting for MySQL to provide a way to …

The project I am working on for Google Summer of Code 2008 is "A Test Scheduler for the MySQL Build Farm Initiative". The MySQL Build Farm Initiative seeks to create an automated environment that tests MySQL in multiple configurations over a powerful, virtual computing grid provided by community member's local machines.

Currently, MySQL developers use an internal system called push-build to test a static set of configurations across a static set of computing resources. My project will take a step towards realizing the MySQL Build Farm; modify push-build to test a dynamic, rather than static, set of configurations and computing resources.

I will do this by creating a management layer that

1. models the configuration space to be tested
2. selects specific configurations from this space to be tested based on programmable coverage criteria
3. packages and distributes build and test scripts to clients who …

The project I am working on for Google Summer of Code 2008 is "A Test Scheduler for the MySQL Build Farm Initiative". The MySQL Build Farm Initiative seeks to create an automated environment that tests MySQL in multiple configurations over a powerful, virtual computing grid provided by community member's local machines.

Currently, MySQL developers use an internal system called push-build to test a static set of configurations across a static set of computing resources. My project will take a step towards realizing the MySQL Build Farm; modify push-build to test a dynamic, rather than static, set of configurations and computing resources.

I will do this by creating a management layer that

1. models the configuration space to be tested
2. selects specific configurations from this space to be tested based on programmable coverage criteria
3. packages and distributes build and test scripts to clients who …