July 26, 2014

The relationship between Innodb Log checkpointing and dirty Buffer pool pages

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 […]

What’s required to tune MySQL?

I got a serendipitous call (thanks!) yesterday asking what would be needed to tune[1] a database for better performance. It is a question that I hear often, but I never thought about answering it in public. Here’s a consolidated version of what I explained during our conversation.

How InnoDB handles REDO logging

Xaprb (Baron) recently blogged about how InnoDB performs a checkpoint , I thought it might be useful to explain another important mechanism that affects both response time and throughput – The transaction log.

MySQL 5.5.8 and Percona Server on Fast Flash card (Virident tachIOn)

This is to follow up on my previous post and show the results for MySQL 5.5.8 and Percona Server on the fastest hardware I have in our lab: a Cisco UCS C250 server with 384GB of RAM, powered by a Virident tachIOn 400GB SLC card. To see different I/O patterns, I used different innodb_buffer_pool_size settings: 13G, […]

How well does your table fits in innodb buffer pool ?

Understanding how well your tables and indexes fit to buffer pool are often very helpful to understand why some queries are IO bound and others not – it may be because the tables and indexes they are accessing are not in cache, for example being washed away by other queries. MySQL Server does not provide […]

Moving from MyISAM to Innodb or XtraDB. Basics

I do not know if it is because we’re hosting a free webinar on migrating MyISAM to Innodb or some other reason but recently I see a lot of questions about migration from MyISAM to Innodb. Webinar will cover the process in a lot more details though I would like to go over basics in […]

Tuning InnoDB Concurrency Tickets

InnoDB has an oft-unused parameter innodb_concurrency_tickets that seems widely misunderstood. From the docs: “The number of threads that can enter InnoDB concurrently is determined by the innodb_thread_concurrency variable. A thread is placed in a queue when it tries to enter InnoDB if the number of threads has already reached the concurrency limit. When a thread […]

Why you should ignore MySQL’s key cache hit ratio

I have not caused a fist fight in a while, so it’s time to take off the gloves. I claim that somewhere around of 99% of advice about tuning MySQL’s key cache hit ratio is wrong, even when you hear it from experts. There are two major problems with the key buffer hit ratio, and […]

Blob Storage in Innodb

I’m running in this misconception second time in a week or so, so it is time to blog about it. How blobs are stored in Innodb ? This depends on 3 factors. Blob size; Full row size and Innodb row format. But before we look into how BLOBs are really stored lets see what misconception […]

The perils of InnoDB with Debian and startup scripts

Are you running MySQL on Debian or Ubuntu with InnoDB? You might want to disable /etc/mysql/debian-start. When you run /etc/init.d/mysql start it runs this script, which runs mysqlcheck, which can destroy performance. It can happen on a server with MyISAM tables, if there are enough tables, but it is far worse on InnoDB. There are […]