It’s been busy here. I’ll announce why soon, but one thing that caught my eye recently that just can’t go by is the imminent open sourcing of DRBD+. DRBD+ is the commercial version of DRBD. This has serious implications for anyone who is serious about building real world cloud applications.

DRBD can be thought of as network-based disk drive mirroring (aka ‘RAID-1’). Essentially, you make sure that all writes to a local disk happen to a remote disk simultaneously or near-simultaneously. Combined with today’s modern journaling filesystems and you have pretty a pretty bullet-proof solution. In the past I’ve used DRBD to build very robust HA clustered appliances and the like. I was also one of the first folks to test it on EC2, although I did not publish results at the time.[1]

DRBD worked extremely well on EC2, but there was always one key drawback: It only mirrors disks between two hosts. Dual redundancy, in this case, isn’t sufficient on EC2. It is quite possible you could lose two hosts; however, the odds of losing three of three are extremely small. That’s where DRBD+ comes in.

One of the most compelling features of DRBD+ is that it allows 3-way or 4-way replication. So, now if you need to build a redundant HA cluster that can not fail on a cloud computing system it’s much much easier than before.

Many kudos to the Linbit team for taking this direction. I think they have opened up an opportunity for cloud solution providers to do some very interesting things.

  1. Works great. Very fast replication on EC2 between nodes. Probably even faster on a hardware virtualization platform like GoGrid or FlexiScale.