Stephane CombaudonStéphane joined Percona in July 2012, after working as a MySQL DBA for leading French companies such as Dailymotion and France Telecom. In real life, he lives in Paris with his wife and their twin daughters. When not in front of a computer or not spending time with his family, he likes playing chess and hiking.
Estimating potential for MySQL 5.7 parallel replication
Unlike MySQL 5.6, where parallel replication can only be used when replicas have several schemas, MySQL 5.7 replicas can read binlog group commit information coming from the master to replicate transactions in parallel even when a single schema is used. Now the question is: how many replication threads should you use? A simple benchmark Let’s […]
RocksDB 101
After we announced that Percona offers support for RocksDB, we saw many people looking for more details about this storage engine. Here is a quick list of some of the most frequent questions we get. Q: What is RocksDB? A: Quoting the homepage of the project: RocksDB is an embeddable persistent key-value store for fast storage. […]
Online DDL and Percona XtraDB Cluster 5.6
I presented a talk at Percona Live Amsterdam a few weeks ago (simple recipes for your Galera cluster), and one of the topics was schema changes. I discussed the drawbacks and benefits of Total Order Isolation (TOI), Rolling Schema Upgrades (RSU) and pt-online-schema-change. One thing I forgot was online DDL from 5.6. Does it provide […]
MongoDB and Percona TokuMX Security Guidelines
Several reports we’re published in the news about how easy it is to access data stored in some NoSQL systems, including MongoDB. This is not surprising because security was rather relaxed in earlier versions of MongoDB . This post lists some of the common vulnerabilities in MongoDB and Percona TokuMX. Network Security One key point […]
super_read_only and GTID replication
Percona Server 5.6.21+ and MySQL 5.7.8+ offer the super_read_only option that was first implemented in WebscaleSQL. Unlike read_only, this option prevents all users from running writes (even those with the SUPER privilege). Sure enough, this is a great feature, but what’s the relation with GTID? Read on! TL;DR Enabling super_read_only on all slaves when using […]
How much could you benefit from MySQL 5.6 parallel replication?
I have heard this question quite often: “At busy times, our replicas start lagging quite frequently. We are using N schemas, so which performance boost could we expect from MySQL 5.6 parallel replication?” Here is a quick way to give you a rough estimate of the potential benefit. General idea In MySQL 5.6, parallelism is […]
The MySQL query cache: Worst enemy or best friend?
During the last couple of months I have been involved in an unusually high amount of performance audits for e-commerce applications running with Magento. And although the systems were quite different, they also had one thing in common: the MySQL query cache was very useful. That was counter-intuitive for me as I’ve always expected the […]
SELinux and the MySQL init script
I recently worked with a customer who had a weird issue: when their MySQL server was started (Percona Server 5.5), if they try to run service mysql start a second time, the init script was not able to detect that an instance was already running. As a result, it tried to start a second instance […]
Percona XtraDB Cluster (PXC): How many nodes do you need?
A question I often hear when customers want to set up a production PXC cluster is: “How many nodes should we use?” Three nodes is the most common deployment, but when are more nodes needed? They also ask: “Do we always need to use an even number of nodes?” This is what we’ll clarify in […]
Percona XtraDB Cluster: Quorum and Availability of the cluster
Percona XtraDB Cluster (PXC) has become a popular option to provide high availability for MySQL servers. However many people are still having a hard time understanding what will happen to the cluster when one or several nodes leave the cluster (gracefully or ungracefully). This is what we will clarify in this post. Nodes leaving gracefully […]
Optimizing Percona XtraDB Cluster for write hotspots
Some applications have a heavy write workload on a few records – for instance when incrementing a global counter: this is called a write hotspot. Because you cannot update the same row simultaneously from multiple threads, this can lead to performance degradation. When using Percona XtraDB Cluster (PXC), some users try to solve this specific […]
Storing time-series data with MongoDB and TokuMX
Storing time-series data is a frequent pattern for databases – be it for logs or for any kind of monitoring. Such data has the following properties: records are inserted but also never updated, the insertion rate can be high and records are likely to expire after some time. MongoDB and TokuMX are both good fits […]
MySQL indexing 101: a challenging single-table query
We discussed in an earlier post how to design indexes for many types of queries using a single table. Here is a real-world example of the challenges you will face when trying to optimize queries: two similar queries, but one is performing a full table scan while the other one is using the index we […]
MongoDB’s flexible schema: How to fix write amplification
Being schemaless is one of the key features of MongoDB. On the bright side this allows developers to easily modify the schema of their collections without waiting for the database to be ready to accept a new schema. However schemaless is not free and one of the drawbacks is write amplification. Let’s focus on that […]
Test your knowledge: Percona XtraDB Cluster (PXC) quiz
I often talk with people who are very interested in the features of Percona XtraDB Cluster (PXC) such as synchronous and parallel replication, multi-node writing and high availability. However some get confused when operating a real PXC cluster because they do not fully realize the implications of these features. So here is a fun way […]
Indexing 101: Optimizing MySQL queries on a single table
I have recently seen several cases when performance for MySQL queries on a single table was terrible. The reason was simple: the wrong indexes were added and so the execution plan was poor. Here are guidelines to help you optimize various kinds of single-table queries. Disclaimer: I will be presenting general guidelines and I do […]
MySQL shell prompt vs MongoDB shell prompt
Recently Todd Farmer shared an interesting story about the mysql command line prompt in MySQL 5.7: how it was changed to provide more context and why the change was finally reverted. This made me think that after using the command line client for MongoDB for awhile, I would love seeing a much more modern mysql […]
Choosing a good sharding key in MongoDB (and MySQL)
MongoDB 3.0 was recently released. Instead of focusing on what’s new – that is so easy to find, let’s rather talk about something that has not changed a lot since the early MongoDB days. This topic is sharding and most specifically: how to choose a good sharding key. Note that most of the discussion will also […]
Q&A: Multi-threaded Replication in MySQL 5.6 and MySQL 5.7
My webinar “Multi-threaded Replication in MySQL 5.6 and 5.7” on February 25 generated several excellent questions following the presentation (available an online migration to GTIDs and that’s why here.