November 29, 2014

keepalived with reader and writer VIPs for Percona XtraDB Cluster

This is a followup to Jay Janssen’s October post, “Using keepalived for HA on top of Percona XtraDB Cluster.” We got a request recently where the customer has 2 VIPs (Virtual IP addresses), one for reader and one for a writer for a cluster of 3 nodes. They wanted to keep it simple, with low […]

Percona Toolkit 2.1.9 is ready

About a month ago, we held a bug raffle for Percona Toolkit 2.1.9.  The turnout was good and the resulting release is worth upgrading to, especially if you were affected by the backwards-incompatible changes to pt-heartbeat in 2.1.8.  Here are the release notes for Percona Toolkit 2.1.9 which highlight the bugs fixed: Percona Toolkit 2.1.9 has been released. […]

Can’t Create Thread: Errno 11 (A Tale of Two Ulimits)

Recently some of my fellow Perconians and I have noticed a bit of an uptick in customer cases featuring the following error message:

The canonical solution to this issue, if you do a bit of Googling, is to increase the number of processes / threads available to the MySQL user, typically by adding a […]

Read/Write Splitting with PHP Webinar Questions Followup

Today I gave a presentation on “Read/Write Splitting with PHP” for Percona Webinars.  If you missed it, you can still register to view the recording and my slides. Thanks to everyone who attended, and especially to folks who asked the great questions.  I answered as many as I could during the session, but here are […]

Sphinx search performance optimization: multi-threaded search

Queries in MySQL, Sphinx and many other database or search engines are typically single-threaded. That is when you issue a single query on your brand new r910 with 32 CPU cores and 16 disks, the maximum that is going to be used to process this query at any given point is 1 CPU core and […]

How to STOP SLAVE on Amazon RDS read replica

We are doing a migration from Amazon RDS to EC2 with a customer. This, unfortunately, involves some downtime – if you are an RDS user, you probably know you can’t replicate an RDS instance to an external server (or even EC2). While it is annoying, this post isn’t going to be a rant on how […]

Differences between READ-COMMITTED and REPEATABLE-READ transaction isolation levels

As an instructor with Percona I’m sometimes asked about the differences between the READ COMMITTED and REPEATABLE READ transaction isolation levels.  There are a few differences between READ-COMMITTED and REPEATABLE-READ, and they are all related to locking.

Percona XtraDB Cluster: Failure Scenarios with only 2 nodes

During the design period of a new cluster, it is always advised to have at least 3 nodes (this is the case with PXC but it’s also the same with PRM). But why and what are the risks ? The goal of having more than 2 nodes, in fact an odd number is recommended in […]

thread_concurrency doesn’t do what you expect

Over the last months I’ve seen lots of customers trying to tune the thread concurrency inside MySQL with the variable thread_concurrency. Our advice is: stop wasting your time, it does nothing on GNU/Linux Some of the biggest GNU/Linux distributions includes the variable thread_concurrency in their my.cnf file by default. One example is Debian and its […]

btrfs – probably not ready yet

Every time I have a conversation on SSD, someone mentions btrfs filesystem. And usually it is colored as a solution that will solve all our problems, improve overall performance and SSD in particular, and it is a saviour. Of course it caught my curiosity and I decided to perform a benchmark similar to what I […]