DSXchange

We currently have 11.5 on a 2 server back end:
- Engine Tier,
- Services Tier (with WebSphere and DB2 for xmeta, dsodb, iadb,esdb, etc).

We are looking to go to a 3 server back end:
- Engine Tier
- WebSphere/Services Tier
- Database Tier

My question is, is there any concerns about putting all the Infosphere databases on the same Database server?
Should Xmeta remain on the WebSphere/Services Tier?
Should IADB (Information Analyzer DB) be on it's own server (we have low volume of IA use currently)?

Just looking from thoughts from people experienced in putting the DB's on a separate servers.

The topology is largely irrelevant provided that there's as fast a link as possible between the metadata repository and services tiers.