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 [...]
A case for MariaDB’s Hash Joins
May 31, 2012 By Leave a Comment
MariaDB 5.3/5.5 has introduced a new join type “Hash Joins” which is an implementation of a Classic Block-based Hash Join Algorithm. In this post we will see what the Hash Join is, how it works and for what types of queries would it be the right choice. I will show the results of executing benchmarks [...]
Troubleshooting MySQL Memory Usage
March 21, 2012 By 5 Comments
One of the most painful troubleshooting tasks with MySQL is troubleshooting memory usage. The problem usually starts like this – you have configured MySQL to use reasonable global buffers, such as innodb_buffer_size, key_buffer_size etc, you have reasonable amount of connections but yet MySQL takes much more memory than you would expect, causing swapping or other [...]
The relationship between Innodb Log checkpointing and dirty Buffer pool pages
February 17, 2012 By 10 Comments
This is a time-honored topic, and there’s no shortage of articles on the topic on this blog. I wanted to write a post trying to condense and clarify those posts, as it has taken me a while to really understand this relationship. Some basic facts Most of us know that writing into Innodb updates buffer [...]
Troubleshooting MySQL Upgrade Performance Regressions
February 15, 2012 By Leave a Comment
So lets say you upgraded from MySQL 5.1 to Percona Server 5.5 and instead of expected performance improvement you see your performance being worse. What should you do ? First if you followed MySQL upgrade best practices such as testing your workload with pt-upgrade the chances of this happening are rather slim. But lets assume [...]
Innodb vs MySQL index counts
November 29, 2011 By 6 Comments
I had a customer recently who a few strange errors in their mysqld.err log:
1 | [ERROR] Table database_name/table_name contains 8 indexes inside InnoDB, which is different from the number of indexes 7 defined in the MySQL |
This customer was running Percona Server 5.1 and they got this error on two tables during a maintenance window when they were adding indexes to the same tables. We had a suspicion that it had something to do with Fast [...]
MySQL Life Cycle. Your Feedback is needed.
November 18, 2011 By 6 Comments
When I started with MySQL 3.22 I would start running MySQL from early beta (if not alpha) and update MySQL the same date as release would hit the web. Since that time I matured and so did MySQL ecosystem. MySQL is powering a lot more demanding and business critical applications now than 12 years ago [...]
Make your file system error resilient
August 24, 2011 By 8 Comments
One of the typical problems I see setting up ext2/3/4 file system is sticking to defaults when it comes to behavior on errors. By default these filesystems are configured to Continue when error (such as IO error or meta data inconsistency) is discovered which can continue spreading corruption. This manifests itself in a worst way [...]
The two even more fundamental performance metrics
May 5, 2011 By 6 Comments
In a recent blog post, I wrote about four fundamental metrics for system performance analysis. These are throughput, residence time, “weighted time” (the sum of all residence times in the observation period — the terminology is mine for lack of a better name), and concurrency. I derived all of these metrics from two “even more [...]
Advanced index analysis with mk-index-usage
November 11, 2010 By 2 Comments
The new release of Maatkit has a useful feature in mk-index-usage to help you determine how indexes are used in more flexible ways. The default report just prints out ALTER statements for removing unused indexes, which is nice, but it’s often helpful to ask more sophisticated questions about index usage. I’ll use this blog’s queries [...]
