December 5, 2013 By Severalnines

Thanks to everyone who attended yesterday’s webinar; if you missed the sessions or would like to watch the webinar again & browse through the slides, they are now available online.

Thanks again to our speaker, Seppo Jaakola from Codership, the creators of Galera Cluster, for this in-depth talk on Galera Cluster Best Practices - Zero Downtime Schema Changes.

Webinar topics covered

• How to perform Zero Downtime Schema Changes
• 2 main methods: TOI and RSU
• Total Order Isolation: predictability and consistency
• Rolling Schema Upgrades
• pt-online-schema-change
…

December 4, 2013 By Severalnines

As OpenStack deployments mature from evaluation/development to production environments supporting apps and services, high-availability becomes a key requirement. In a previous post, we showed you how to cluster the database backend - which is central to the operation of OpenStack. In that setup, you would have two controllers, while placing a 3-node Galera cluster on separate hosts. Now, it can be quite a leap to go from one VM with all services running on it, to a fully distributed setup with 5 VMs. The good news is that you can have a highly available setup starting with just 3 VMs.

In this post, we are going to show you how to cluster OpenStack Havana in a minimal node setup with 2 controllers and one compute node. Our controllers will be running all OpenStack services, as well as clustered RabbitMQ …

November 14, 2013 By Severalnines

Database schema changes are usually not popular among DBAs or sysadmins, not when you are operating a cluster and cannot afford to switch off the service during a maintenance window. There are different ways to perform schema changes, some procedures being more complicated than others. We invited Seppo from the Codership team to tell us about the options. If you’d like to learn more, please register for our new webinar.

Webinar: Galera Cluster Best Practices - Zero Downtime Schema Changes

Tuesday, December 3rd 2013

Register now - Europe/MEA/APAC

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November 4, 2013 By Severalnines Percona Live London MySQL Conference - 11-12th November, 2013

We’re particularly excited about this year’s Percona Live London MySQL Conference. The line-up of speakers & topics looks excellent and it’s good to see speakers from Oracle, Percona, the MariaDB Foundation (amongst others) scheduled at the same event. It demonstrates not just the diversity of the ever broadening MySQL ecosystem, but also the fact that there really is room for everyone to contribute, participate in and advance MySQL in manifold directions while still retaining a certain amount of uniformity.

And this is how we will be contributing to the event ...

Talk - MySQL Cluster Performance Tuning By Johan Andersson, CTO & Co-Founder, Severalnines

Correct tuning of MySQL NDB Cluster can have dramatic impact on …

October 28, 2013 By Severalnines

Data protection is vital for DB admins, especially when it involves data that is accessed and updated 24 hours a day. Clustering and replication are techniques that provide protection against failures, but what if a user or DBA issues a detrimental command against one of the databases? A user might erroneously delete or update the contents of one or more tables, drop database objects that are still needed during an update to an application, or run a large batch update that fails midway. How do we recover lost data? 

In a previous post, we showed you how to do a full restore from backup. Great, now you’ve restored up to the last incremental backup that was done at 6am this morning. But how about the rest of the data?

This is where you’d do a …

October 23, 2013 By Severalnines

Last week, the Severalnines & Codership teams came together to co-host two webinar sessions on Galera 3.0, MySQL 5.6, Global Transaction IDs and WAN. The sessions were held during EMEA/APAC as well as NA/LATAM timezones, which worked out quite nicely. Our speakers were Seppo Jaakola from Codership & Vinay Joosery from Severalnines. 

Webinar topics:

• Galera Cluster features and benefits
• Support for MySQL 5.6
• Integration with MySQL Global Transaction Identifiers
• Mixing Galera synchronous replication and asynchronous MySQL replication
• Deploying in WAN and Cloud …

October 16, 2013 By Severalnines

Galera uses a preallocated file with a specific size called gcache, used to store the writesets in circular buffer style. By default, its size is 128MB. In this post, we are going to explore how to leverage gcache to improve the operation of a Galera cluster.

Test Case

We have a four node Galera cluster, using the latest release 23.2.7(r157). We have a table called t1 that is replicated by Galera on all nodes. The cluster nodes have allocated the default 128MB gcache.size, and we’ll try to execute a large writeset to see how gcache responds.

mysql> SHOW VARIABLES LIKE …

September 24, 2013 By Severalnines

For those of you who know Severalnines and maybe use some of our tools & products, you’ll know that we provide our users with a monthly summary of all the resources & tools that we’re publishing. Since this is publicly available material, we thought it’d be useful also for the broader open source database community.

In the past month, we’ve made the following resources & tools available: 

• Troubleshooting MySQL Cluster (free online MySQL Cluster Training)
• Zero Downtime Data Center Migration with Galera
• ClusterControl 1.2.3 Released
• High Availability OpenStack - Clustering the Database Backend
• NoSQL Battle of the East Coast - Benchmarking MongoDB vs TokuMX Cluster
• Full restore of a Galera Cluster from Backup

  …

September 17, 2013 By Severalnines

Galera cluster has known limitations, one of them is that it uses cluster-wide optimistic locking. This may cause some transactions to rollback. With an increasing number of writeable masters, the transaction rollback rate may increase, especially if there is write contention on the same dataset. It is of course possible to retry the transaction and perhaps it will COMMIT in the retries, but this will add to the transaction latency. However, some designs are deadlock prone, e.g sequence tables. In this blog we present how you can minimize the risk for deadlocks due to the design of Galera. 

Test Case

Here is a simple test case. We have a table that contains a column and a row that hold a number and is regularly updated to provide …

July 2, 2013 By Severalnines

Joomla! is estimated to be the second most used CMS on the internet after WordPress, with users like eBay, IKEA, Sony, McDonald’s and Pizza Hut. In this post, we will describe how to scale Joomla on multiple servers. This architecture not only allows the CMS to handle more users, by load-balancing traffic across multiple servers. It also brings high availability by providing fail-over between servers.

This post is similar to our previous posts on web application scalability and high availability:

• Drupal - Apache, MySQL Galera Cluster, csync2 with lsyncd
• Wordpress - Apache, Percona XtraDB Cluster, …