High Availability Solution?

Hello, I am new to Informix and wanted to get more information about their HA solutions. This will be a a Linux platform. I come from DB2 so I am familiar with their solutions (HADR, PureScale). I have found some information about the following for Informix but I was a little confused : 1) HDR (seems to be the same as DB2's HADR) 2) Mach 11 - (HDR but can have more than one secondary and those secondaries allow read and write operations? requires dedicated servers?) 3) Innovator C - (also HDR but has only one secondary that allows read and write operations) ? good for a two node setup but not scalable? I think I understand HDR but not sure I understand Mach 11 or Innovator C and what their difference is. Does anyone know a very good writeup on those or can explain the main points on the two? I am looking for an active/active type solution that can scale horizontally and maybe even vertically. DB2's HADR doesnt scale well beyond two nodes. PureScale scales horizontally but is very cumbersome (requires a lot of expensive add ons like dedicated servers and infiniband network system). Your input is appreciated.