Has your database (or mail or file) server crashed? Is your entire department waiting for you to restore service? Are your most recent backups a month old? Are those backups off-site? Is this a frighteningly real scenario? Oh, yeah. Can it be avoided? Oh, yeah. The Distributed Replicated Block Device (DRBD) system can save the day, your data, and your job. DRBD provides data redundancy at a fraction of the cost of other solutions.
Almost every service depends on data. So, to offer a service, its data must be available. And if you want to make that service highly-available, you must first make the data it depends on highly-available.
The most natural way to do this (and hopefully, it’s something you already do on a regular basis) is to backup your data. In case you lose your active data, you just restore from the most recent backup, and the data is available again. Or, if the host your service runs on is (temporarily) unusable, you can replace it with another host configured to provide the identical service, and restore the data there.
To reduce possible downtime, you can have a second machine ready to takeover.
Whenever you change the data on one machine, you back it up on the other. You can have the secondary machine switched off, and just turn it on if the primary host goes down. This is typically referred to as cold standby. Or you can have the backup…
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