April 20, 2014

Percona XtraDB Cluster – installation and setup webinar follow up Q&A

Thanks for all, who attended my webinar, I got many questions and I wanted to take this opportunity to answer them. Q: Even ntp has a delay of 0.3-0.4 between servers does that mean a 0.25 as from logs can be an issue ? A: My demo vms were running for a few hours before […]

Filling the tmp partition with persistent connections

The use of tmpfs/ramfs as /tmp partition is a common trick to improve the performance of on-disk temporary tables. Servers usually have less RAM than disk space so those kind of partitions are very limited in size and there are some cases were we can run out of space. Let’s see one example. We’re running […]

Troubleshooting MySQL Memory Usage

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 […]

How to Monitor MySQL with Percona’s Nagios Plugins

In this post, I’ll cover the new MySQL monitoring plugins we created for Nagios, and explain their features and intended purpose. I want to add a little context. What problem were we trying to solve with these plugins? Why yet another set of MySQL monitoring plugins? The typical problem with Nagios monitoring (and indeed with […]

Setting up XFS on Hardware RAID — the simple edition

There are about a gazillion FAQs and HOWTOs out there that talk about XFS configuration, RAID IO alignment, and mount point options.  I wanted to try to put some of that information together in a condensed and simplified format that will work for the majority of use cases.  This is not meant to cover every […]

Reasons for MySQL Replication Lag

One common theme in the questions our MySQL Support customers ask is MySQL Replication Lag. The story is typically along the lines everything is same as before and for some unknown reason the slave is started to lag and not catching up any more. I always smile at “nothing has changed” claim as it usually […]

Aligning IO on a hard disk RAID – the Theory

Now that flash storage is becoming more popular, IO alignment question keeps popping up more often than it used to when all we had were rotating hard disk drives. I think the reason is very simple – when systems only had one bearing hard disk drive (HDD) as in RAID1 or one disk drive at […]

Impact of the sort buffer size in MySQL

The parameter sort_buffer_size is one the MySQL parameters that is far from obvious to adjust. It is a per session buffer that is allocated every time it is needed. The problem with the sort buffer comes from the way Linux allocates memory. Monty Taylor (here) have described the underlying issue in detail, but basically above […]

InnoDB memory allocation, ulimit, and OpenSUSE

I recently encountered an interesting case. A customer reported that mysqld crashed on start on OpenSUSE 11.2 kernel 2.6.31.12-0.2-desktop x86_64   with 96 GB RAM when the innodb_buffer_pool_size was set to anything more than 62 GB. I decided to try it with 76 GB. The error message was an assert due to a failed malloc() […]

Upgrading MySQL

Upgrading MySQL Server is a very interesting task as you can approach it with so much different “depth”. For some this is 15 minutes job for others it is many month projects. Why is that ? Performing MySQL upgrade two things should normally worry you. It is Regressions – functionality regressions when what you’ve been […]