mysql clustering database replication vs file-based replication ( mysql+drbd+heartbeat )

You have a low budget to implement mysql clustering, i suggest you to choose Heartbeat+DRBD. I have used my old server (PIII+512Mb) to developt MySQL Clustering. I only need 2 server to implement this clustering method compared with MySQL Clustering use replication method you'll need at least 4 server and you also need good hardware with big memory size to implement this clustering.

Need to know more about MySQL Replication concept? You may check Mysql Clustering white paper.