Everything is a Freaking DNS problem

For those who've seen my presentation on MySQL HA, you already know that I often use a multimaster setup with a meta OCF resource that groups my favoured MySQL instance with the service ip , using a meta resource means that pacemaker monitors mysql, but it doesn't actually manage it. It's an approach that works for us.

One of the other approaches I will be looking at soon is the freshly released OCF resource that Florian announced last week.

Back in the days our approach meant we didn't have to use clone resources, which you might remember being pretty buggy in the v2 era, not wanting to use clons resources isn't really a valid reason anymore these days . I've also frequently mentioned the combination of using DRBD and MultiMaster replication, using this set of OCF resource makes that a lot more easy ..

Now all I need to do is find me some time to validate this setup.

Funny how different experiences lead to different evaluations of tools. The MySQL HA solutions the MySQL Performanceblog list, are almost listed in the complete opposited order of what my impressions are.

Ok agreed, I should probably not put my MySQL NDB experiences from 2-3 years ago with multiple Query of deaths and more problems than you into account anymore , but back then went in the list Less stable than a single node. I've had NDB POC setups going down for much more than 05:16 minutes
Ndb comes with a lot of restrictions, there are

As for MySQL on DRBD, I've said this before , I love DRBD, but having to wait for a long InnoDB recovery after a failover just kills your uptime ,
I remember being called by a customer during Fred last holiday who was waiting over 20 minutes for recovery , twice, so putting the DRBD/San setup second would not be my preference. But agreed .. it's only listed at 99.9% meaning almost 9 hours of downtime per year are allowed.

On the other hand we've seen database uptime of MySQL MultiMaster setups with Heartbeat reaching better figures than 99.99% Heck I've seen single nodes achieve better than 99.99% :)

So what does this teach us ... there is no golden rule for HA, lots of situations are different, it's the preferences of the customer, the size of the database, the kind of application , and much
more .. you always need to think and evaluate the environment ...

Lenz just posted pointers to a great presentation of his about MySQL HA and Drupal,

Seems like a small part of me did go to Szeged afterall :)

Apart form the Xen book I coauthored earlier this year the nice folks of the MySQL documentation team asked me to review parts of their MySQL Cluster Certification guide.

After a long wait it's finally out !
In contrary to the other one, this book took over a year to finish because there was actually a lot of reviewing done by different people.

You can buy it now at Lulu.com !

John might want to read it to figure out about his 5th step.

So Sun bought ClusterFS. I`m wondering what their focus will be now. What will be the prime platform on which Lustre will be developed Solaris or Linux ? Will other efforts in the open source cluster filesystem area react on this ? Will Lustre development speed up ? Will management become less complex ?
Time will tell .. I`m keeping an eye on it

Sunday evening was the conference dinner, someone tought he was really funny to have us all walk about 3Km more than we needed to. The instructions on the back of our entrance tickets gave us a full tour of the Cambridge suburbs, I should have followed my guts.. not the people trying to read the instructions, would have saved us half an our at least .
Luckily we took the short way back. Dinner was typically english .. nuff said :)

So monday started out with a whole bunch of sessions related to filesystems and storage.
Bryn M Reeves gave a really good intro to LVM , then Jan Blunck took over and started talking about how to scale the Device Mapper snap shot solution. I tried to see Dag's talk on dstat but I`ll have to try again at T-Dose as I missed the largest part of the talk due to some phone calls :(
Next up was Olaf "thank god I`m not doing nfs anymore" Kirch (who also listens when you just shout Lars in the streets of Cambridge) who introduced us to iSNS.

So after lunch the filesystem track continued with Steven Whitehouse talking about VFS and cluster filesystems , Jorn talking to us about the future of Flashdisks ant their appropriate filesystems, and Chris Mason from Oracle finishing of with a talk on Btrfs.. pronounced "ButterFS"

There were 2 different busses to the Duxford air museum which was a bit of a pity since both groups didn't really meet eachother, so it wasn't really a social event where you could chat and meed with everybody at the conference.

I already mentionned ganeti before when going over the LinuxConference Europe Schedule
Google just poste the news a couple of hours ago and you can go and check out the project on Google Code

Quoting from their site :

"Ganeti is a virtual server management software tool built on top of Xen virtual machine monitor and other Open Source software.
However, Ganeti requires pre-installed virtualization software on your servers in order to function. Once installed, the tool will take over the management part of the virtual instances (Xen DomU), e.g. disk creation management, operating system installation for these instances (in co-operation with OS-specific install scripts), and startup, shutdown, failover between physical systems. It has been designed to facilitate cluster management of virtual servers and to provide fast and simple recovery after physical failures using commodity hardware. "

You can use disk management using either plain LVM volumes, local-disk raid1 mirrors or across-the-network raid1 (using DRBD) for quick recovery in case of physical system failure

I`ll certainly be in the talk next week and I`ll be keeping a look on what happens ..