October 23, 2014

MySQL and the SSB – Part 2 – MyISAM vs InnoDB low concurrency

This blog post is part two in what is now a continuing series on the Star Schema Benchmark. In my previous blog post I compared MySQL 5.5.30 to MySQL 5.6.10, both with default settings using only the InnoDB storage engine.  In my testing I discovered that innodb_old_blocks_time had an effect on performance of the benchmark.  There was […]

Virident vCache vs. FlashCache: Part 2

This is the second part in a two-part series comparing Virident’s vCache to FlashCache. The first part was focused on usability and feature comparison; in this post, we’ll look at some sysbench test results. Disclosure: The research and testing conducted for this post were sponsored by Virident. First, some background information. All tests were conducted […]

Return of the Query Cache, win a Percona Live ticket

It’s Friday again, and time for another TGIF give-away of a Percona Live London ticket! But first, what’s new with the MySQL query cache? You may know that it still has the same fundamental architecture that it’s always had, and that this can cause scalability problems and locking, but there have been some important changes […]

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 […]

More on table_cache

In my previous post I looked into how large table_cache actually can decrease performance. The “miss” path is getting more expensive very quickly as table cache growths so if you’re going to have high miss ratio anyway you’re better off with small table cache. What I have not checked though is how does table_cache (or […]

table_cache negative scalability

Couple of months ago there was a post by FreshBooks on getting great performance improvements by lowering table_cache variable. So I decided to investigate what is really happening here. The “common sense” approach to tuning caches is to get them as large as you can if you have enough resources (such as memory). With MySQL […]

Crashes while using MyISAM with multiple key caches

Over last couple of years I have ran into random MySQL crashes in production when multiple key caches were used. Unfortunately this never was frequent or critical enough issue so I could spend time creating repeatable test case and search of the bug in the MySQL database did not find anything. Recently we had this […]

Getting annoyed with MyISAM multiple key caches.

As I’ve wrote few times using multiple key caches is a great way to get CPU scalability if you’re using MyISAM. It is however very annoying – this feature really looks half baked to me. The problem with multiple key caches and mapping of tables to the different files is – there is no way […]

Using Multiple Key Caches for MyISAM Scalability

I have written before – MyISAM Does Not Scale, or it does quite well – two main things stopping you is table locks and global mutex on the KeyCache. Table Locks are not the issue for Read Only workload and write intensive workloads can be dealt with by using with many tables but Key Cache […]

Beware of MyISAM Key Cache mutex contention

Today I was working with the client loading data to MyISAM tables at very high rate. Hundreds of millions rows are loaded daily into single MySQL instance with bursts up to 100K of records/sec which need to be inserted (in the table with few indexes). It was good not all records had to go to […]