We recently run into some troubles with max_allowed_packet size problems during backups with the FromDual Backup/Recovery Manager and thus I investigated a bit more in the symptoms of such problems.

Hello oli,

every user/process on a UNIX system has some user limits. There are some soft (S) and hard (H) user limits. Soft limits a user can change himself up to the hard limits.

Hello oli,

it looks like you have enabled skip_name_resolve in your my.cnf.
This prevents MySQL to do (DNS) host lookups. If you have created some users with explicit host names MySQL wants to tell you now that you cannot use these users any more with this configuration. Example:

Looking at Percona Server source code we can find the following:

For processing SELECT queries MySQL needs some times the help of temporary tables. These temporary tables can be created either in memory or on disk.

After properly installing and testing a Galera Cluster we see that the set-up is not finished yet. It needs something in front of the Galera Cluster that balances the load over all nodes.
So we install a load balancer in front of the Galera Cluster. Typically nowadays HAProxy is chosen for this purpose. But then we find, that the whole Galera Cluster is still not high available in case the load balancer fails or dies. So we need a second load balancer for high availability.
But how should we properly failover when the HAProxy load balancer dies? For this purpose we put a Virtual IP (VIP) in front of the HAProxy load balancer pair. The Virtual IP is controlled and failovered with Keepalived.

We have recently seen a case where the following command was executed on a Galera Cluster node:

Precaution: Before you try this out on your production system do a BACKUP first! FromDual Backup Manager can help you with this.

This week, we did some migrations from MariaDB 10.0 to Percona Server 5.6 at the IT department of a big German bank.

Sometimes it could be desirable to replicate from a Galera Cluster to a single MySQL slave or to an other Galera Cluster. Reasons for this measure could be:

Will you be at a loss having a MySQL or MariaDB database problem? Will you need urgently help from experienced FromDual staff when your production MySQL or MariaDB database stops working? Or do you need a third party opinion for one of your MySQL or MariaDB solutions?

Hello,

there are companies which earn tens of thousands of Euros per hour with their MySQL databases. Other companies operate their ERP system on MySQL, to which 1000 employees are attached to. Is the database down 1000 people are not working any more until the system is working again! Downtime costs starting at EUR 30'000.- per hour upwards.

Thanks, Morgan!

MySQL single query performance - the truth!

As suggested by morgo I did a little test for the same query and the same data-set mentioned in Impact of column types on MySQL JOIN performance but looking into an other dimension: the time (aka MySQL versions).

Hi Morgan,

Thanks!

I have planed such a test already a while ago but did not find the time to do it yet...

In our MySQL trainings and consulting engagements we tell our customers always to use the smallest possible data type to get better query performance. Especially for the JOIN columns. This advice is supported as well by the MySQL documentation in the chapter Optimizing Data Types:

If you are not operating MySQL databases yourself, but you develop MySQL based software, our MySQL development support is exactly fitting to your needs!

Features

Galera is a synchronous multi-master replication Cluster for MySQL/InnoDB databases, having features like:

Hello csmanioto,

As mentioned above this is a PoC and should never be used on system with critical data because it is an evil hack!!!

Great News: Galera Cluster v3.1 GA for MySQL 5.6 was released at Percona Live London (PLUK) 2013. The information is still a bit hidden…