DRBD (a registered trademark of LINBIT, who maintain the project) is a solution for redundant data storage within HA setups. It enables you to mirror data from one server over to another, keeping it available even if one of the two servers fails.

We're probably the most experienced DRBD experts you can find. Florian was the original author and maintainer of the DRBD User's Guide, the authoritative reference on DRBD (he has since resigned that role). All of us have deployed DRBD in many different settings and under highly diverse requirements.

What's it good for?

Basically, HA setups are pointless without data redundancy. You must ensure that all your data is just as highly available as your application servers.

There are several approaches to data redundancy. Native SAN replication is usually quite expensive and locks you to a specific vendor. Host-based mirroring with SAN storage often requires redundant fibre links, adding to cost. Application specific replication requires you to learn and deploy multiple distinct (and incompatible) replication facilities in a single stack.

DRBD follows a superior approach: it's a Linux kernel module that enables application-agnostic data replication between two standard, off-the-shelf servers. Think RAID1 device, albeit mirrored between two hosts over a network connection.

HA, DR or both: you decide!

DRBD supports synchronous, semi-synchronous and asynchronous replication. It supports partial, bitmap-based resynchronization and multi-site replication. This makes DRBD extremely useful in high availability, disaster recovery, and combined configurations.

Is it available on my system?

DRBD was integrated into the mainline Linux kernel in February 2009 and comes with almost all modern Linux distributions. Ubuntu and Debian GNU/Linux ship it out of the box, and in SLES, it's part of the High Availability Extension (HAE). On RHEL, it is available as a supported third-party module, and CentOS ships it routinely.

Suffering from strange effects or poor performance while using DRBD? We can help with DRBD consulting services. Straight away. Ask The Expert Now!