There is much more to write about all the work we do at Facebook with memory management efficiency on our systems, but there was this one detour investigation in the middle of 2012 that I had to revisit recently courtesy of Wikipedia.

There are lots of factors that make machines page out memory segments into disk, thus slowing everything down and locking software up – from file system cache pressure to runaway memory leaks to kernel drivers being greedy. But certain swap-out scenarios are confusing – systems seem to have lots of memory available, with proper settings file system cache should not cause swapping, and obviously in production environment all the memory leaks are ironed out.

And yet in mid-2012 we noticed that our new kernel machines were swapping out for no obvious reason. When it comes to swapping, MySQL community will always point to Jeremy’s post on …

This is a followup to Jay Janssen’s October post, “Using keepalived for HA on top of Percona XtraDB Cluster.” We got a request recently where the customer has 2 VIPs (Virtual IP addresses), one for reader and one for a writer for a cluster of 3 nodes. They wanted to keep it simple, with low latency and does not require an external node resource like HaProxy would.

keepalived is a simple load balancer with HA capabilities, which means it can proxy TCP services behind it and at the same time, keep itself highly available using VRRP as failover mechanism. This post is about taking advantage of the …

Many installations of MySQL server come with a built-in database called test. It's initially empty, and you might wonder what it's for, or even if you can delete it without any problems.

What is it for? 

The test database is installed by the MySQL Server RPM as part of the mysql_install_db process, and some other package managers run that script too. If you run that script as part of a manual install of MySQL, you'll get the same effect. It creates the database by creating an empty directory called "test" in the data directory, and creates wide-open access to the database test and any database with a name beginning with test_ by inserting a couple of rows into the mysql.db table that give everyone full access to create or use those databases.

The configuration is designed to make it easy for new users to create a playground or sandbox database to work with, one that doesn't require asking the DBA …

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Many installations of MySQL server come with a built-in database called test. It's initially empty, and you might wonder what it's for, or even if you can delete it without any problems.

What is it for? 

The test database is installed by the MySQL Server RPM as part of the mysql_install_db process, and some other package managers run that script too. If you run that script as part of a manual install of MySQL, you'll get the same effect. It creates the database by creating an empty directory called "test" in the data directory, and creates wide-open access to the database test and any database with a name beginning with test_ by inserting a couple of rows into the mysql.db table that give everyone …

For this year’s Percona Live: MySQL Conference and Expo 2014 (PLMCE), Davi Arnaut and I submitted a couple of co-speaking sessions proposals, both of which were accepted. Please come and see us and learn some more about InnoDB at the following sessions:

InnoDB: A journey to the core II

In this new installment of the series, we explore the most crucial structures for crash recovery and consistency, the redo and undo logs. This presentation dissects the structure and organization of InnoDB’s redo and undo logs, providing insight into how data changes occur at the InnoDB layer and how it guarantees that it can recover to a consistent state in the event of a crash. This …

As you might have noticed—at least if you have read SQL Performance Explained—I don’t think clustered indexes are as useful as most people believe. That is mainly because it is just too darn difficult to choose a good clustering key. As a matter of fact, choosing a good—the “right”—clustering key is almost impossible if there are more than one or two indexes on the table. The result is that most people just stick to the default—which is the primary key. Unfortunately, this is almost always the worst possible choice.

In this article I explain the beast named clustered index and all it’s downsides. Although this article uses SQL Server as demo database, the article is equally relevant for MySQL/MariaDB with InnoDB and the Oracle database when using index-organized tables.

Recap: What is a clustered index

The idea of clustered …

MySQL data rules the cloud, but recent experience shows us that there's no substitute for maintaining copies of data, across availability zones and regions, when it comes to Amazon Web Services (AWS) data resilience. In this webinar, we discuss the multi-master capabilities of Continuent Tungsten to help you build and manage systems that spread data across multiple sites. 

We cover topics such

FOSDEM is coming to town again here in Brussels this February 1-2, and as usual, there is a MySQL Devroom. Traditionally, a MySQL and Friends community dinner is also held during the event and this year is no different – we’ve organized one for Saturday, February 1 from 8:30 p.m. to 11:30 p.m. (CET).

If you want to sign up for the dinner, go to http://fosdemmysqlcommunitydinner2014.eventbrite.com/

This year’s edition is going to be slightly different…

We have rented a private cafeteria at a company called Mundo-B, where catering will be served by …

Regarding virtualization I am a LXC guy. Nevertheless Docker has won a lot of attention and I would like to show how to use MySQL with Docker.

What is Docker?

In fact Docker is a wrapper around LXC. It is fun to use. Docker has the philosophy to virtualize single applications using LXC. So in our example we are going to start a mysqld in a chroot environment encapsulated in his own Namespaces. (You can even set Cgroups resources.) One of the main points regarding Docker is the usage of a union filesystem (aufs). So when you start a Docker Container it gets his aufs mount and only changed data is written down.

Aufs is great for a lot of applications and sufficient for Database testing. I just want to share a simple - more educational, than effective - Dockerfile. Dockerfiles are the buildscripts for the Docker images.

Lets have a look at the Dockerfile:

FROM ubuntu
MAINTAINER erkan yanar …

This blog, MySQLPerformanceBlog.com, is powered by WordPress, but we never really looked into what kind of queries to MySQL are used by WordPress. So for couple months we ran a Query Analytics (part of Percona Cloud Tools) agent there, and now it is interesting to take a look on queries. Query Analytics uses reports produced by pt-query-digest, but it is quite different as it allows to see trends and dynamics of particular query, in contrast to pt-query-digest, which is just one static report.

Why looking into queries important? I gave an intro in my previous post from this series.

So Query Analytics give the report on the top queries. How to detect which query is “bad”?
One of metrics I am typically looking into is ratio of “Rows …