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Changing the Tablespace Directory with pt-online-schema-change

In this blog, we’ll discuss changing the tablespace directory using pt-online-schema-change.

One of the most annoying situations in the life of a DBA is realizing that the disk where the datadir resides is running out of space. If you’re lucky enough to run over an LVM volume or a RAID (depending on the level, though), it is easy to add disk space. But what if you are not that lucky, and your datadir is running on a single disk? Not so funny!

That is the exact situation we recently faced with a customer, for both the master and slave server. When trying to figure out a solution we saw that:

  • There was enough space on a different partition within the same server.
  • The tables have their own tablespace (innodb_file_per_table = on)
  • The MySQL version was …
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Open-sourcing Rocksplicator, a real-time RocksDB data replicator

Pinterest’s stateful online systems process tens of petabytes of data every day. As we build products and scale billions of Pins to 150 million people, we need new applications that work in a way where computation co-locates with data. That’s why we adopted RocksDB. It’s adaptable, supports basic and advanced database operations with high performance and meets the majority of requirements for building large-scale, production-strength distributed stateful services. Yet two critical pieces were missing for us: real-time data replication and cluster management for RocksDB-based stateful services. To fill this gap, we built a RocksDB replicator–Rocksplicator–a cluster management library, as well as tools for RocksDB-based stateful services. Today we’re open-sourcing the project on GitHub for all RocksDB users. 

Before we dive into Rocksplicator, …

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Separation of Query Server and Data Server

In MySQL we have separated the Query Server and the Data Server
functionality. The Query Server is what takes care of handling the
SQL queries and maps those to lower layers call into the Data Server.
The API to the Data Server in MySQL is the storage engine API.

Almost all DBMS have a similar separation between Data Server and Query

When I performed my research work, that later led to development of
NDB Cluster, that is now MySQL Cluster, an important part of the
research was to handle the separation of the Data Server and
the Query Server.

As part of my research we looked deeply into the next generation mobile
networks and their use of network databases. From these studies it was
obvious that the traffic part of the applications almost always made very
simple queries, mostly key lookups and in some cases slightly more …

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MySQL can be evil

Ok, maybe evil is too strong a word, but MySQL can certainly be deceiving.

MySQL can be evil

Ok, maybe evil is too strong a word, but MySQL can certainly be deceiving.

Orchestrator: Moving VIPs During Failover

In this post, I’ll discuss how to moving VIPs during a failover using Orchestrator.

In our previous post, we showed you how Orchestrator works. In this post, I am going to give you a proof-of-concept on how Orchestrator can move VIPs in case of failover. For this post, I’m assuming the Orchestrator is already installed and able to manage the topology.


Orchestrator is a topology manager. Nothing less nothing more. In the case of failover, it will reorganize the topology, promote a new master and connect the slaves to it. But it won’t do any DNS changes, and it won’t move VIPs (or anything else).

However, Orchestrator supports hooks. Hooks are external scripts …

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FromDual.en: FromDual Performance Monitor for MySQL and MariaDB 1.0.0 has been released

FromDual has the pleasure to announce the release of the new version 1.0.0 of its popular Database Performance Monitor for MySQL, MariaDB, Galera Cluster and Percona Server fpmmm.

You can download fpmmm from here.

In the inconceivable case that you find a bug in fpmmm please report it to our Bug-tracker.

Any feedback, statements and testimonials are welcome as well! Please send them to

This release contains various bug fixes and improvements. Further significant functionality has changed and improved. So please read carefully...

Changes in fpmmm v1.0.0

fpmmm agent

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MySQL Replication: All the Severalnines Resources

As many of you will know, MySQL Replication has become an instrumental part of scale-out architectures in LAMP environments. MySQL offers plenty of solutions when there is a need to scale out, the most common being to add read replicas. The major bottleneck for our data is generally not so much oriented around writing our data but more around reading it back. Therefore the easiest way to scale MySQL is to add replicas for reading.

We’ve produced a number of resources during the course of this year aimed at helping users to get started with MySQL Replication and/or get more out of their existing setups.

We’ve summarised these resources here in a handy overview, so that you can pick and chose the ones that might be the most relevant to you.

Do check them out and let us know your feedback!

The White Papers The MySQL© Replication Blueprint by Severalnines

This is a great resource for anyone wanting to …

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MySQL Server bootstrapping and dictionary initialization

In MySQL 8.0, we are making large changes to the way the MySQL server stores meta data with the introduction of our native data dictionary. As part of these improvements, we have also made changes to the way the server bootstraps.…

MySQL Architecture and Components

This blog post is all about new MySQL 5.7 physical, logical architecture and it’s components.In this blog post, I will try to explain things in flow including data processing and SQL execution in MySQL with the help of diagrams.

Unlike the other databases ,MySQL is a very flexible and offers different kinds of storage engines as a plugin for different kinds of needs. Because of this, MySQL architecture and behavior will also change as per the use of storage engines, for example transactional [InnoDB] and non-transactional [MyISAM] engines data storage and SQL execution methods will be different and within the server it will use engine specific components like memory and buffers depending on type storage engine will get used for the SQL operation.
Will discuss more about InnoDB, since it’s default and main storage engine for MySQL.

MySQL Physical Architecture: Configuration …

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