The other day, I was discussing high availability (HA) with other people.  The discussion was going in the direction of, as the application was only using INSERT ... ON DUPLICATE KEY UPDATE (ODKU) and traffic could be replayed, promoting a slave in case of the failure of the master was easy: replaying traffic would make all the slaves converge back to a common state.  It looks as this could work but it might not be as simple.  Before going into the details, let's take a step back and look into HA in general.

tl;dr: be careful when using row-based replication when replicating ODKU as slaves will stop replicating if a row is present on the master and missing on slave (or vice-versa).

High Availability by Promoting a Slave as the new Master
Let's suppose we are working …

August 13, 2014 By Severalnines

New Webinar: Performance Tuning of HAProxy for Database Load Balancing

Date, Time & Registration: 

Tuesday, September 9th @10am CEST (Europe & MEA / Asia Pacific)

Register here

Tuesday, September 9th …

Actually, I found this error many times, while installing MySQL/Percona servers with MySQL Sandbox.

To resolve this issue, first, you have to make sure that, SSL is installed /update properly.

sudo apt-get update
sudo apt-get install libssl1.0.0 libssl-dev

After installing this you have to create appropriate link to make it work.

For 32 bit

cd /usr/lib/
sudo ln -s libssl.so.1.0.0 libssl.so.6
sudo ln -s libcrypto.so.1.0.0 libcrypto.so.6

For 64 bit:

cd /usr/lib/x86_64-linux-gnu
sudo ln -s libssl.so.1.0.0 libssl.so.6
sudo ln -s libcrypto.so.1.0.0 libcrypto.so.6

Normally this should work for CentOS and Debian too but If in Debian, it didn’t worked then do this.

sudo ln -s /usr/lib/x86_64-linux-gnu/libssl.so.1.0.0 /usr/lib/libssl.so.6
sudo ln -s /usr/lib/x86_64-linux-gnu/libcrypto.so.1.0.0 /usr/lib/libcrypto.so.6

I’m sure, it will work.

…

Tue, 2014-08-12 19:25anderskarlsson

We all know that in general it's a bad idea to have columns values contain too much "hidden" information, and in particular for primary keys, this is a big no-no, although I know that not everybody agrees here. In some cases though, there is data that at it's heart contains several aspects and we just cannot avoid this, the prime example being data and time values. What I mean here is that a single datetime value has aspects that aren't always obvious from the datetime value itself. Examples include leap year information and weekday. Sometimes datetime value also contain the timezone, in which case you might want to ask if this is the timezone of the server or the client.

Can you make a datetime unique? Let's assume you know that every row that contains a datetime value are at least 5 ms apart, from which you can determine that if the datetime is stored with ms precision, you will always get …

MariaDB 10.0.13 was recently released, and is available for download here:

https://downloads.mariadb.org/mariadb/10.0.13/

This is the fourth GA release of MariaDB 10.0, and 14th overall release of MariaDB 10.0.

This is primarily a bug-fix release.

Here are the main items of note:

1. InnoDB upgraded to 5.6.19.
2. XtraDB upgraded to 5.6.19-67.0.
…

August 12, 2014 By Severalnines

Moodle is an open-source e-learning platform (aka Learning Management System) that is widely adopted by educational institutions to create and administer online courses. For larger student bodies and higher volumes of instruction, moodle must be robust enough to serve thousands of learners, administrators, content builders and instructors simultaneously. Availability and scalability are key requirements as moodle becomes a critical application for course providers. In this blog, we will show you how to deploy and cluster moodle/web, database and file-system components on multiple servers to achieve both high availability and scalability. 

We are going to deploy moodle on top of GlusterFS clustered file system and MariaDB Galera Cluster 10. To eliminate any single point of failure, we will use three nodes to serve the application and database while the remaining two are used for …

Diablo Technologies engaged Percona to benchmark IBM eXFlash™ DIMMs in various aspects. An eXFlash™ DIMM itself is quite an interesting piece of technology. In a nutshell, it’s flash storage, which you can put in the memory DIMM slots. Enabled by Diablo’s Memory Channel Storage™ technology, this practically means low latency and some unique performance characteristics.

These devices are special, because their full performance potential is unlocked by using multiple devices to leverage the parallelism of the memory subsystem. In a modern CPU there is more than one memory controller (4 is typical nowadays) and spreading eXFlash™ DIMMs across them will provide maximum performance. There are quite some details about the device that are omitted in this post, they can be found in this redbook.

Diablo technologies also provided us a …