zrep provides an easy-to-use program to manage zfs filesystem replication and failover. No configuration files are required. The program is developed under Solaris, but may work with any up to date zfs implementation. The executable is a single script. Initialization does a full data copy, but subsequent syncs are incrementals. It uses internal locking to make sure there is no danger of overlap if you just shove it in cron to run every minute. Design target is more "near-time replication", since the sync can be run every minute or more. However, it could conceivably be used for "backup" purposes as well.
NexentaStor is a unified storage solution that installs on standard hardware and provides enterprise class storage at a fraction of the cost of legacy, proprietary storage solutions. NexentaStor is particularly well suited for virtualized environments thanks to the ability of NexentaStor to eliminate duplication of primary data storage, to manage the storage for virtual environments from one interface, and to leverage SSDs to address the random I/O and boot storm issues with virtual environments.