Shinguz's blog

As you probably have experienced yet MySQL does not always provide all internal information as you might want to have them and as you are used to have from other RDBMS.

The following summary shows my personal understanding of MySQL 5.1 licenses, packages and products. It does not necessarily reflect 100% the way MySQL understands it. But after all the discussions I hope it is as close as possible to the reality:

[http://www.blogger.com/profile/11195863756524022642 Shinguz] said…

Hey guys,

Have a look at the addendum. I have updated it.

This week we had a very interesting problem at a customer: They complained, that their MySQL Cluster takes about 1 hour for a --initial start-up. After some tuning on the hardware and the config.ini they brought it down to around 40 minutes. But this is still unacceptable long…

[http://www.blogger.com/profile/11195863756524022642 Shinguz] said…

Hi Baron

Hmmm. Did not know about it. But to be honest: I did not yet have time to look at all the nice stuff from your Maatkit and all the cool Google Patches and OurDelta etc… :-(

[http://www.blogger.com/profile/11195863756524022642 Shinguz] said…

Hi Willy

Yes. MySQL circular replication usually works fine (technically). I hope you have a good concept cleaning it up again when it some how messes up!

Introduction

One of the features that make MySQL so great is its easy replication set-up. If you are experienced and know-how to do it, it takes you about 15 minutes to set-up a slave. What you have in the end is a replication from one master to one or several slaves. So you can build a top-down data stream pyramid and spread your data on many slaves.

When I set-up a MySQL HA environment for customers I usually do some final failover tests after configuring the whole beast.

Das dreieckige Rad hat gegenüber dem viereckigen einen gewaltigen Vorteil: Ein Rumms weniger pro Umdrehung!

[http://www.blogger.com/profile/11195863756524022642 Shinguz] said…

Hi knetknight

Thanks for your comment.

When your are facing time/scheduling issues I recommend you to go through the MySQL online documentation (Chapter: Table Maintenance Statements and Restrictions on InnoDB Tables) because some of these commands have no effect on some table types (InnoDB) and some of them do the work already done in a previous command.

[http://www.blogger.com/profile/11195863756524022642 Shinguz] said… Hi Matthew

Thanks for your comment. This could have helped a lot. I do NOT ask why there was no message like:

Recently we were migrating an InnoDB/MyISAM schema to NDB. I was too lazy to calculate all the needed MySQL Cluster parameters (for example with ndb_size.pl) and just took my default config.ini template.

A customer has recently experienced a possible memory leak in its NDB-API application. What he did was something like:

Electing a slave as new master and aligning the other slaves to the new master

In a simple MySQL Replication set-up you have high-availability (HA) on the read side (r). But for the master which covers all the writes (w) and the time critical read (rt) there is no HA implemented. For some situations this can be OK. For example if you have rarely writes or if you can wait until a new Master is set up.

The following maintenance jobs are typically run against a MySQL database:

According to Johans wishes I write down my concerns about MySQL (Cluster) replication. These items are things I run again and again into it with customers:

The parameter DiskSyncSize is a MySQL Cluster parameter and was added in MySQL 5.1.23.

Sometimes it is nice to show customers the functionality of MySQL-Enterprise Monitor (aka Merlin). I install the agents on the servers and the dashboard runs on my laptop. But very often only ssh is open to these servers.

What is a sparse file?

“A sparse file is a file where space has been allocated but not actually filled with data. These space is not written to the file system. Instead, brief information about these empty regions is stored, which takes up much less disk space. These regions are only written to disk at their actual size when data is written to them. The file system transparently converts reads from empty sections into blocks filled with zero bytes at runtime.”
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A friend of me asked me long time ago: “How can I have a ranking on a result with MySQL?”. Now I found some time to write it down: