Here's my presentation I gave June 9, 2008, at the Twin Cities MySQL and PHP User Group about my highly available cluster using DRBD and Heartbeat.

I added a few slides and cleaned things up a bit. The presentation went well and we had a lot of good questions.

The MySQL and PHP User Group will be taking some time off over the summer. There will be another meetup mid-summer to come up with some ideas for future meetings.

Here's my presentation I gave June 9, 2008, at the Twin Cities MySQL and PHP User Group about my highly available cluster using DRBD and Heartbeat.

I added a few slides and cleaned things up a bit. The presentation went well and we had a lot of good questions.

The MySQL and PHP User Group will be taking some time off over the summer. There will be another meetup mid-summer to come up with some ideas for future meetings.

Yesterday I went to beCamp 2008 along with four roomfuls of other people interested in technology (perhaps close to 100 people total). The conference was a lot of fun. Not everything went as planned, but that was as planned. This was an Open Spaces conference and I thought it worked very well. From an email Eric Pugh sent:

Basically it all boils down to:

Open Space is the Law of Two Feet: if anyone finds themselves in a place where they are neither learning nor contributing they should move to somewhere more productive. And from the law flow four principles:

• Whoever comes are the right people
• Whatever happens is the only thing that could have
• Whenever it starts is the right time
…

Florian is replying to James on the subject of using DRBD for MySQL HA. A discussion started earlier by Eric Florian is refuting most of the arguments that James has against using MySQL and DRBD together.

I`m also saying NO to MySQL and DRBD in most of the cases.. but not for any of the reasons James mentions.

I must say upfront I love DRBD and I have been using it in production for a long time but not for MySQL HA.

The problem with using MySQL on DRBD is the same problem you have when killing the power on a standalone MySQL machine and rebooting that machine.
DRBD saves you the time of powering up your machine and OS. But MySQL …

The day of tutorials started out with All Bases Covered: A Hands-on Introduction to High-availability MySQL and DRBD by Florian Haas and Philipp Reisner.

After a brief introduction to DRBD, they started discussing the configuration file. There were a couple settings that I had set incorrectly on my servers.

Since I have my two servers connected via a gigabit crossover cable, I had my synchronization rate set to 125MB. They recommended approximately 1/3 your network and disk I/O so that you're applications don't freeze up during synchronization. Their test system used 30MB so I'll give it a try too.

Another setting they had different was the activity log extents. All of the references I looked at said to set the al-extents …

One of the concepts of clustering, is that the secondary node may need to stonith the primary node in a forced take over in order to make it give up shared resources. This works great on more expensive hardware that has a management interface like IPMI, but my 'toys' budget is a little more limited.

It's equally possible to just cut the node off at it's power source. Does anyone know of a (cheap) power strip with a serial[1]/usb[1]/network interface where I can send signals to cut off individual ports power?

If I can't switch off individual power ports, I will need to buy two and have the nodes each manage the opposite node's power.

[1] If it's serial or USB I'll need to use a third node as a proxy to the device, which is annoying, but quite possible.

Yesterday Phillip Reisner was giving an introduction to DRBD. I won't get into it here, but essentially it's a way to keep blockdevices on two different hosts in sync to get a kind of shared disk. (Go read about it on their site!)

I've used it for a while to get high-availability from two NFS servers and I always recommend it in my scalability talk. It's awesome. (Heartbeat which is the "fail-over" software in the typical configuration isn't so great, more on that another time).

Anyway, being at the MySQL conference the context of course is "how can this be used for MySQL". Usually I prefer a simpler master-master replication setup for redundancy. Later in the afternoon Mats Kindahl (one of the replication …