October 20, 2014

How to avoid hash collisions when using MySQL’s CRC32 function

Percona Toolkit’s  pt-table-checksum performs an online replication consistency check by executing checksum queries on the master, which produces different results on replicas that are inconsistent with the master – and the tool pt-table-sync synchronizes data efficiently between MySQL tables. The tools by default use the CRC32. Other good choices include MD5 and SHA1. If you have installed the FNV_64 user-defined function, pt-table-sync will […]

MySQL Replication: ‘Got fatal error 1236′ causes and cures

MySQL replication is a core process for maintaining multiple copies of data – and replication is a very important aspect in database administration. In order to synchronize data between master and slaves you need to make sure that data transfers smoothly, and to do so you need to act promptly regarding replication errors to continue […]

OpenStack users shed light on Percona XtraDB Cluster deadlock issues

I was fortunate to attend an Ops discussion about databases at the OpenStack Summit Atlanta this past May as one of the panelists. The discussion was about deadlock issues OpenStack operators see with Percona XtraDB Cluster (of course this is applicable to any Galera-based solution). I asked to describe what they are seeing, and as […]

Monitoring MySQL flow control in Percona XtraDB Cluster 5.6

Monitoring flow control in a Galera cluster is very important. If you do not, you will not understand why writes may sometimes be stalled. Percona XtraDB Cluster 5.6 provides 2 status variables for such monitoring: wsrep_flow_control_paused and wsrep_flow_control_paused_ns. Which one should you use? What is flow control? Flow control does not exist with regular MySQL replication, […]

Q&A: Even More Deadly Mistakes of MySQL Development

On Wednesday I gave a presentation on “How to Avoid Even More Common (but Deadly) MySQL Development Mistakes” for Percona MySQL Webinars.  If you missed it, you can still register to view the recording and my slides. Thanks to everyone who attended, and especially to folks who asked the great questions.  I answered as many as we had […]

A conversation with 5 Facebook MySQL gurus

Facebook, the undisputed king of online social networks, has 1.23 billion monthly active users collectively contributing to an ocean of data-intensive tasks – making the company one of the world’s top MySQL users. A small army of Facebook MySQL experts will be converging on Santa Clara, Calif. next week where several of them are leading […]

Measuring Max Replication Throughput on Percona XtraDB Cluster with wsrep_desync

Checking throughput with async MySQL replication Replication throughput is the measure of just how fast the slaves can apply replication (at least by my definition).  In MySQL async replication this is important to know because the single-threaded apply nature of async replication can be a write performance bottleneck.  In a production system, we can tell […]

Innotop: A real-time, advanced investigation tool for MySQL

GUI monitoring tools for MySQL are not always suitable for all our needs or situations. Most of them are designed to provide historical views into what happens to our database over time rather then real-time insight into current MySQL server status. Excellent free tools for this include Cacti, Zabbix, Ganglia, Nagios, etc. But each of […]

Tuning MySQL 5.6 configuration – Webinar followup

We had a wonderful time during the Sept. 25 webinar, “MySQL 5.6 Configuration Optimization,” and I got a lot more questions than I could answer during the hour. So here is a followup with answers to the most interesting questions you guys asked. (You can also watch a recording of entire webinar here.) Q: What […]

Amazon RDS with MySQL 5.6 – Configuration Variables

One longstanding complaint I have heard for the past several years, and still hear today, is that Amazon’s Relational Database Service (RDS) does not allow the configuration flexibility as running MySQL in an ec2 instance. While true, this ignores the consistent work that Amazon has done to provide access to the most important configuration variables […]