HAST allows to transparently store data on two physically separated machines connected over the TCP/IP network. Those two machines together will be called a cluster and each machine is one cluster node. HAST works in Primary-Secondary (Master-Backup, Master-Slave) configuration, which means that only one of the cluster nodes can be active at any given time. Active node will be called Primary node. This is the node that will be able to handle I/O requests to HAST-managed devices. Currently HAST is limited to two cluster nodes in total.
Imagine putting PostgreSQL on a FreeBSD system running ZFS within a cluster running HAST.
Now that’s a great combination of open source solutions.