What is most valuable?
The replication technology is very fast and efficient. If you can live with an active-passive setup, DRBD will be an awesome storage replication solution. For a while now also a multi-master setup is possible. It is different from the traditional use of DRBD, though.
How has it helped my organization?
DRBD helped keep data synchronized between multiple nodes and multiple nodes in different datacenters. This alone is great; however, if you need to failover between two nodes, DRBD is very fast and efficient. DRBD helped me and many customers to provide data in an HA environment with low costs (since DRBD itself is free).
What needs improvement?
Working with DRBD can be complex and it takes time to understand how it works. Especially split-brain scenarios need to be handled carefully. When it comes to multi-master setups, which are possible with the latest DRBD version, you need to use a cluster filesystem. I think that DRBD should write their own filesystem which can be used in multi-master environments since most cluster filesystems are complex or simply have many flaws.
For how long have I used the solution?
I have been using DRBD for 5 years.
What was my experience with deployment of the solution?
The deployment is not very difficult, so no issues were encountered.
What do I think about the stability of the solution?
No, even under high load DRBD seems to be rock-solid and stable.
What do I think about the scalability of the solution?
Well, until the latest version of DRBD, it was only possible to run DRBD in a two-node setup. This makes scaling difficult, of course.
Which solution did I use previously and why did I switch?
There is no real alternative - if you need a very good active-passive storage solution and don't want to buy a storage appliance, DRBD is the way to go.
What about the implementation team?
I always implemented it myself.
What's my experience with pricing, setup cost, and licensing?
Support for DRBD is very expensive, but you get the real experts.
What other advice do I have?
Make sure to use the latest version possible and that DRBD really fits your requirements. Also make sure to gain enough knowledge so you can react in a proper way if something goes wrong (e.g. unexpected failover).