I learned something new about myisamchk. When doing a recovery of the data file, it creates not one but two temporary files. I knew about the TMD it creates in $datadir when rebuilding the MYD file but it creates a second temporary file using an old and rather annoying technique (which involves creating a file using the standard C ‘open()’ call, then deleting the file without closing the file descriptor.) I discovered this when myisamchk told me “Disk is full writing ‘/tmp/STQ3p9UF’ (Errcode: 28).” I looked in /tmp and didn’t see that file. So I did a

# lsof | grep delete

and low-and-behold, there it was. You know, as a sys admin, that really annoys me. I don’t care that it creates temporary files to do its thing. In fact, I expect it, but I at least want to know about it so I can plan accordingly. My /tmp partition only had 2.5 gigs of space and the table’s MYD was over 4 gigs in size. If I had known …

Here is some of my thoughts on migrating MySQL to Sql Server. It came out of an email discussion. I’d love to hear your thoughts on migrating to a different database platform, not just MySQL to Sql Server.

I actually thought about writing a white paper or even a course on migrating from MySQL to Sql Server, but never got the time to do it. Sometimes a project doing similar things can serve as a launchpad for this endeavour, but that never came along, at least not yet. I am very interested in database interoperability field though. I’ve done MySQL and Oracle admin in the past and have published some MySQL and Oracle stuff in blogs. I have much better technical skills on Sql Server than any other RDBMS platforms, primarily because I’ve worked on it longer.

Here are some of my thoughts. I think most of it applies equally on migration from Oracle, DB2, Sybase, Postgresql, etc., to Sql Server, or the other way around. It …

At $WORK we typically use Redhat Cluster to make MySQL highly available. We have a number of 2-node clusters (active/passive) and it works nicely, for the most part. One thing I find very annoying is RHCS has no notification framework to notify you when a service is relocated to another node (because of failure or otherwise.)

In a perfect world, the only reason MySQL would pass between nodes is for server maintenance, under the control of a human. In reality, crap happens. Redhat Cluster manages all this, but I still want to know that a failover happened (is hardware going bad? did a software bug cause a failure? etc.)

Most monitoring tools weren’t designed to report on a clustered service. I can add a check that connects to MySQL using the cluster-managed IP - but that only tells me if MySQL has failed completely. The failover between nodes generally takes under a minute so it’s easy for that type of monitoring check to miss a …

Jay Pipes blogged about this earlier this month. I read his post, nodded a knowing nod and finished my cup of coffee. It wasn’t until yesterday when it really struck me. I was looking through the database schema of a popular forum software package (won’t say which) when I came across this column definition in a central table (by ‘central’ I mean one that typically holds a lot of rows):

ip varchar(100),

One hundred characters to store a at-most 15-character IPv4 string? I know what you’re about to say, “But, it’s a varchar so you’re not really using 100 bytes.” Well, you *might* not be. Jay’s discussion on how MySQL uses temporary tables illustrates how you can use all 100 bytes in memory - not a good thing.

So, the minimum number of bytes you will be using is 7 if …

Finally got around to creating a project on Sourceforge: MyHelper. Right now, it’s just some stored procedures and functions for determining data and index sizes for databases using the MyISAM and InnoDB engines. Each one is individually licensed (using the BSD license.) I have 2 more stored procedures to add (return a list of tables with no primary key and a list of tables with the primary key) but I haven’t committed my changes to Subversion yet because I’m still testing them. I’ll be adding more code as I refine the stuff I’ve written over the years (their current state is highly environment-specific so I need to “genericise” them - if that’s a word.)
A word about licensing. I’m opting to license each script/procedure/function individually. This is because the project, as a whole, is made up of individual pieces that may or may not have a dependency …

If you follow the MySQL world at all, or you just have your eyes open, you have probably noticed that an agreement has been reached for Sun to acquire MySQL AB for about one billion dollars. Quite a few people have asked for my thoughts on the matter, so I will provide them publicly here for all. Overall, I see this as a mostly good thing.

I think that Sun has a very good chance of leading MySQL better than MySQL. At the same time, it’s always disconcerting to see a project managed within a very large company. Having been through the large company picture once already, I know how wrongly things can go when too many people (especially management types) are involved in a project.

At the same time, though, I’ve always liked Sun, and have high …

"Didn't see that one coming. Their blog contains details to what this could mean for both companies. May as well be one of the most important takeovers of 2008 already!"

read more | digg story

Could this mean that the mysql cluster is finally going to get proper development attention? I don't know but sure as hell hope so. Congratulations to all mysql employees!

Similar Posts:

• Must-Know People In The MySQL Field
• MySQL Conference Liveblogging: Performance Guide For MySQL Cluster …

This article contains my notes and detailed instructions on setting up a MySQL cluster. After reading it, you should have a good understanding of what a MySQL cluster is capable of, how and why it works, and how to set one of these bad boys up. Note that I'm primarily a developer, with an interest in systems administration but I think that every developer should be able to understand and set up a MySQL cluster, at least to make the dev environment more robust.

Notes

• High availability. If one or some of the machines go down, the cluster will stay up, as long as there is at least one copy of all data still present. The more redundant copies of data there are, the more machines you can afford to lose.
• Scalability. Distributed architecture allows for load balancing. If your MySQL …

Today I was (again) facing a log file from a machine that had for some reason not been able to start a temporary MySQL daemon during the night to prepare for a streaming MySQL slave installation. The necessary 2nd daemon had created its new ibdata files, however just after that aborted the startup process with the following message:

Can't start server: Bind on TCP/IP port: No such file or directory
071001 23:09:55 [ERROR] Do you already have another mysqld server running on port: 3310 ?
071001 23:09:55 [ERROR] Aborting
071001 23:09:55 [Note] mysql\bin\mysqld.exe: Shutdown complete

As you can see, the port is a different one from the default MySQL port, so I can be sure there was no conflict with the primary instance. Even more curiously the same process has been working on that and other machines flawlessly for some …