April 21, 2014

How Does Semisynchronous MySQL Replication Work?

With the recent release of Percona XtraDB Cluster, I am increasingly being asked about MySQL’s semi-synchronous replication. I find that there are often a number of misconceptions about how semi-synchronous replication really works. I think it is very important to understand what guarantees you actually get with semi-synchronous replication, and what you don’t get. The […]

MySQL Limitations Part 3: Subqueries

This is the third in a series on what’s seriously limiting MySQL in certain circumstances (links: part 1, 2). This post is about subqueries, which in some cases execute outside-in instead of inside-out as users expect.

READ-COMMITED vs REPETABLE-READ in tpcc-like load

Question what is better isolation level is poping up again and again. Recently it was discussed in InnoDB : Any real performance improvement when using READ COMMITED isolation level ? and in Repeatable read versus read committed for InnoDB . Serge in his post explains why READ COMMITED is better for TPCC load, so why […]

Finding your MySQL High-Availability solution – Replication

In the last 2 blog posts about High Availability for MySQL we have introduced definitions and provided a list of ( questions that you need to ask yourself before choosing a HA solution. In this new post, we will cover what is the most popular HA solution for MySQL, replication.

MySQL Replication vs DRBD Battles

Well these days we see a lot of post for and against (more, more) using of MySQL and DRBD as a high availability practice. I personally think DRBD has its place but there are far more cases when other techniques would work much better for variety of reasons. First let me start with Florian’s comments […]

Is disk Everything for MySQL Performance ?

I read very nice post by Matt today and it has many good insights though I can’t say I agree on all points. First there is a lot of people out where which put it as disk is everything. Remember Paul Tuckfield saying “You should ask how many disks they have instead of how many […]

State of MySQL Market and will Replication live ?

There are interesting posts these day about future of MySQL Replication by Brian Frank and Arjen. I think it very interesting to take a look at a bit bigger picture using framework from Innovators Dilemma and Innovators Solution. I’m not going to speak about disruption and commoditisation of Database Market, leaving this for Market talks, […]

MySQL should have dynamic durability settings

If you’re using Innodb tables MySQL has innodb_flush_log_at_trx_commit variable which defines how durable your transactions are. If you have high durability requirements you set it to 1 and log records are pushed directly to the disk on transaction commit. If you do not bother loosing come committed transactions you can set it to 0 and […]

MySQL 4 to MySQL 5 Upgrade performance regressions

This week I already had two serious performance regression cases when upgrading from MySQL 4.0 and 4.1 to MySQL 5.0. By serious I mean several times performance difference not just 5-10% you often see for simple queries due to generally fatter code. The problem in both cases was MySQL 5.0 broken group commit bug. First […]

MySQL Crash Recovery

MySQL is known for its stability but as any other application it has bugs so it may crash sometime. Also operation system may be flawed, hardware has problems or simply power can go down which all mean similar things – MySQL Shutdown is unexpected and there could be various inconsistences. And this is not only […]