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 [...]
Updated msl (microslow) patch, installation walk-through!
April 20, 2008 By 17 Comments
For a couple of months there have been no updates to our msl patch, however recently I managed some time to change this. The functionality was extended a little bit and what’s even more important the patch is available for all the recent MySQL releases. To remind anyone who has not yet come across this [...]
MySQL Error Message Nonsenses
March 16, 2008 By 7 Comments
What MySQL honestly was never good at is giving good helpful error messages. Start with basics for example – The error message in case of syntax error gives you information about tokens near by but little details:
1 2 | mysql> select * from user oder by pwd; ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'by pwd' at line 1 |
It would be much better if MySQL would give error give exact position of error (with complex [...]
Evaluating IO subsystem performance for MySQL Needs
March 5, 2008 By 23 Comments
I’m often asked how one can evaluate IO subsystem (Hard drive RAID or SAN) performance for MySQL needs so I’ve decided to write some simple steps you can take to get a good feeling about it, it is not perfect but usually can tell you quite a lot of what you should expect from the [...]
What is the longest part of Innodb Recovery Process ?
December 20, 2007 By 1 Comment
In MySQL 4.1 and above the longest part of recovery after crash for Innodb tables could be UNDO stage – it was happening in foreground and was basically unbound – if you have large enough transaction which needed to be undone this could take long hours. REDO stage on other hand always could be regulated [...]
10+ Ways to Crash or Overload MySQL
November 13, 2007 By 20 Comments
People are sometimes contacting me and asking about bugs like this which provide a trivial way to crash MySQL to the user with basic privileges and asking me what to do. My answer to them is – there is nothing new to it and they just sit should back and relax Really – there are [...]
Heikki Tuuri answers to Innodb questions, Part II
November 4, 2007 By 13 Comments
I now got answers to the second portions of the questions you asked Heikki. If you have not seen the first part it can be found here. Same as during last time I will provide my comments for some of the answers under PZ and will use HT for original Heikkis answer. Q26: You also [...]
Figuring out what limits MySQL Replication
March 7, 2007 By Leave a Comment
Today I was cloning the master using LVM Snapshot and found it was taking quite a while to catch up, which highlighted replication could be the limiting factor for this system quite soon, so I decided to check what is limiting MySQL Replication speed. My first idea was to check it based on slow query [...]
Content delivery system design mistakes
February 11, 2007 By 9 Comments
This week I helped dealing with performance problems (part MySQL related and part related to LAMP in general) of system which does quite a bit of content delivery, serving file downloads and images – something a lot of web sites need to do these days. There were quite a bit of mistakes in design for [...]
Slow Query Log analyzes tools
September 6, 2006 By 84 Comments
MySQL has simple but quite handy feature – slow query log, which allows you to log all queries which took over define number of seconds to execute. There is also an option to enable logging queries which do not use indexes even if they take less time (–log-queries-not-using-indexes) Slow query log is great to spot [...]
