Can we build a direct attached storage by taking a computer/server, adding an HBA, and installing some appropriate software? We would use Debian as a host OS for both the DAS and the server.

If so, what software do we use? And do we simply need a HBA for the DAS and the Server? Or do we need more hardware?

The goal is to use an older server that does not have enough room for drives but does have ECC memory, server processors, redundant power supplies, dual nics, etc. Then find any boxes, server or not, the key being having enough room for 8-12 drives, fans, etc. and turning them into a DAS; build two of these DAS's and have them connected to the server.

Eventually we want to have two servers using DRBD and associated services like heartbeat and pace maker to create an HA setup for our server(s) but that will take a long time to configure since I have no experience with anything related to DRBD (yet) and have a learning curve I have to get past, not to mention the additional cost of more hardware (two servers vs one).