High Availability (HA) – MySql using DRBD Part 2

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December 20, 2008
  

TOC — High Availability – DRBD & MySql

  1. High Availability (HA) – MySql using DRBD Part 1
  2. High Availability (HA) – MySql using DRBD Part 2
  3. High Availability (HA) – MySql using DRBD Part 3
  4. High Availability (HA) – MySql using DRBD Part 4
  5. High Availability (HA) – MySql using DRBD Part 5
  6. High Availability (HA) – MySql using DRBD Part 6
  7. High Availability (HA) – MySql using DRBD Part 7

Now lets understand how DRBD works and how it makes copy of data over the network.

You can get little bit of understanding from the picture (taken from drbd website). This picture involves number of technical terms which will help you understand how DRBD works on low level.

If I try to give an overview, I would say:

DRBD is a module close to linux kernel which takes care of data while it is getting written on disk and copy it also on the backup disk on peer node using the peer DRBD installation on peer node.

It actually creates a virtual device in /dev directory which is /dev/drbd0 and this device acts as a wrapper of local disk and backup disk on other machine with the help of DRBD modules on both machines.

There are so many facts and concepts involved in its working but in essence DRBD takes care of backup of your data on other machine which is connected through network so that in case your machine goes down you can bring up the backup machine with almost no loss of your data.

Generally database and files are used to keep valuable information about an application and these are stored on file system and then on disk. DRBD takes care of replicating this information so you become safe about any situation of abrupt shutdown of your main machine.

I used DRBD for some set of files and MySql database which are only data in the application. Rest all components are mainly without state and can be run on any server (main server or backup server).

Installation and Configuration of DRBD in next part. Thanks for visiting.

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