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