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Content Tagged with ha + MySQL

In a lot of environments.

Peter gives a nice overview why you don't always need to invest in big fat redundant hardware.

We've tackled the topic last year already ..

Now I often get weird looks when I dare to mention that Raid is obsolete ..people fail to hear the "in a lot of environments"

Obviously the catch is in the second part, you won't be doing this for your small shop around the corner with just one machine. You'll only be doing this in an environment where you can work with a redundant array of inexpensive disks. Not with a server that has to sit in a remote and isolated location.

Next to that there are situations where you will be using raid, but not for redundancy, but for disk throughput.

In this article, we're going to go through the entire process of installing, configuring and testing DRBD, Heartbeat and MySQL running in a 2 node cluster environment.

A beautiful howto about MySQL, DRBD and Heartbeat

highly available cluster using DRBD and Heartbeat.

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When you connect a Linux server to a SAN, the network driver will present the available SAN partition as normal SCSI drives. This can be more complicated when more than one Fiber Channel paths are involved. Let’s consider a server having two FC adapters (or a dual port one) and a SAN having two FC channels. For this server, each SAN partitions will appear four times but some FC adapter drivers, like the QLogic ones, will filter them out.

If you are using another brand of Fiber Channel adapters, like Emulex, you will see all of them. I recently worked on a MySQL project using 9 SAN partitions so I ended up dealing with 36 SCSI devices (/dev/sdb to /dev/sdao). Dealing with so many devices is not a fun task, especially if the order of the disks is not preserved between after a reboot. My first attempt to deal with this problem was to use partition label and mount partition by label. Although this solution worked, it was slow and I sometimes got errors. Then I found a much better solution, the Linux multipath tool. This tool uses the Linux device mapper architecture and is able to sort out which SCSI devices are the same SAN partition. At the end, you end up with devices similar to /dev/mapper/mpath0 and you mount these devices.