dm-cache is (albeit still classified “experimental”) is in the just released Linux 3.9 kernel. It deals with generic block devices and uses the device mapper framework. While there have been a few other similar tools flying around, since this one has been adopted into the kernel it looks like this will be the one that you’ll be seeing the most in to the future. It saves sysadmins the hassle of compiling extra stuff for a system.

A typical use is for an SSD to cache a HDD. Similar to a battery backed RAID controller, the objective is to insulate the application from latency caused by the mechanical device, the most laggy part of which is seek time (measured in milliseconds). Giventhe  relatively high storage capacity of an SSD (in the hundreds of GBs), this allows you to mostly disregard the mechanical latency for writes and that’s very useful for database systems such as MariaDB.

That covers writes (for the moment), but …

This is the required post about things I observed during this years MySQL conference.

Things that are awesome:

• The tables in sessions. I think these were here last year. They are still awesome this year.
• The new style power plugs. They solved the problem of people tripping over daisy chained power strips and the strips being accidentally turned off.
• Massive quantities of coffee and real cream.

Things that can be improved:

• Lunch tickets. I overheard the same conversation a dozen times about people not being able to find their lunch tickets or not really knowing about them.
• Make badges reversible. A badge under observation will be facing the wrong way.

Things that just bumped me:

• The music is different this year. Now it makes me feel like a teenager struggling with a breakup.
• My secret clean bathroom has been …

MySQL Sandbox has been updated again. The latest version is 3.0.38, which was just released. There were four releases in the space of one week, and this last one is just a polished edition.

Cherry-picking from the Change log:

• Added option --bind_address to complement the effects of --remote_access;
• The script 'enable_gtid' (for MySQL 5.6 +) now is durable. Previously the changes did not survive a restart.
• Now you can install MariaDB with its bizarre version '10.0'
• It also works well with MySQL 5.7. A bug prevented the creation of 'enable_gtid', but it …

In my ongoing quest to completely understand InnoDB’s data storage, I came across a quite small and inconsequential waste, which is nevertheless fun to write about. I noticed the following block of pages which were allocated very early in the ibdata1 system tablespace but apparently unused (unnecessary lines removed from output):

$ innodb_space -f ibdata1 space-page-type-regions

start       end         count       type                
13          44          32          ALLOCATED           

Background on the doublewrite buffer

Most people using InnoDB have heard of the “doublewrite buffer”—part of InnoDB’s page flushing strategy. The doublewrite buffer is used as a “scratch area” to write (by default) 128 pages contiguously before flushing them out to their final destinations (which may be up to 128 different writes). The MySQL …

I attended the OpenWest Conference in Orem, Utah, and have to say its one of the best community organised conferences. There were over 840+ people at the conference (with more walk-in’s), representing a greater than 100% growth rate compared to last year’s conference.

I gave a talk about MariaDB, and its safe to say that we’ve got many new features that that it’s getting very hard to go in-depth in a span of an hour.

One of the highlights for me was attending talks. I give so many talks, and spend a lot of time talking to people about MariaDB and MySQL, that I very rarely get to see other talks or learn new things. So OpenWest was very welcome from that aspect.

On Thursday, I saw a wonderful …

A few days ago I was doing some cleanup on a passive master database using the MySQL client. I didn't want my commands to be replicated so I executed set sql_log_bin=0 in my session.

One of my queries dropped an unused schema that I knew was corrupt, so I wasn't too surprised when the drop database command crashed the MySQL server. After the crash, the server came back up quickly, and my client automatically reconnected, so it was safe to keep running queries right?

Wrong.

When the client reconnected I lost my session state, so sql_log_bin reverted to 1, and any commands I ran from that point forward would be replicated, which I did not want.

This behavior makes sense, and it's documented in the manual:

Automatic reconnection can be convenient because you need not …

A few days ago I was doing some cleanup on a passive master database using the MySQL client. I didn't want my commands to be replicated so I executed set sql_log_bin=0 in my session.

One of my queries dropped an unused schema that I knew was corrupt, so I wasn't too surprised when the drop database command crashed the MySQL server. After the crash, the server came back up quickly, and my client automatically reconnected, so it was safe to keep running queries right?

Wrong.

When the client reconnected I lost my session state, so sql_log_bin reverted to 1, and any commands I ran from that point forward would be replicated, which I did not want.

This behavior makes sense, and it's documented in the manual:

Automatic reconnection can be convenient because you need not …

This is the first screen after a sucessful Drupal 7.22 install.

Drupal is a content management system that runs at least 2.1% of all websites(1). It is easy to use, extensable with over 20,000 add-ons, and runs beautifully with a LAMP stack.

At the heart of most Drupal sites is a MySQL database with, as of Version 7.22, 76 tables. Recently I was asked what needs to be done to a ‘generic’ Drupal to get it running on MySQL 5.6. It is a very easy update that provides better performance, security, and allows access to the newest MySQL 5.6 updates.

For this example, the generic box is a two CPU Dell x86_64 box running Centos 6.4. This is fairly typical of what a low-end hosted system from one of the many web hosting businesses a small busines might rent. Centos 6.4 was installed.

Now to use Yum to get the with the …

For those that wonder what is really going on with MySQL inside Oracle I invite you to read Tomas Ulin Inside MySQL Blog

Stayed tuned for more to come later.

Hi,

It has been a while since I last posted, but I wanted to post about my teams NEW blog page.

New System QA Blog

As always, we look for ways to improve QA and your feedback is always welcomed.
Best Wishes,
/Jeb