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Bidirectional replication--when servers at both sites send and receive data--is another key consideration when selecting a host-level replication software product. With bidirectional replication, a company can run different apps on the servers at each site, but also use those same servers to protect data from the other site.
|Host-based replication software|
|Click here for a comparison of Host-based replication software (PDF).|
File-system and block-based products give admins different options for handling replication between the target and source server. For instance, BakBone's file-system-based NetVault:Replicator includes a global bidirectional parameter, which lets admins select specific directories on the source server they want to include or exclude for replication to the target server and vice versa. This prevents any changes to files on the target server from being replicated to the source server. NetVault:Replicator also includes an option that lets an admin configure all files in all selected directories on both the source and target servers to stay in sync regardless of which server a file change occurred on.
One of the key benefits that file-system products offer over block-based products for bidirectional replication is that they require less storage. Block-based products, such as Softek Storage Solutions Corp.'s Replicator, require dedicated volumes of at least the same size on both the source and target servers. If the source server has a 100GB volume and the target server has a 500GB volume, the source server then needs a 500GB volume to receive replicated data from the target server; the target server would need a 100GB volume for the source server's data for bidirectional replication to work, regardless of what the actual utilization is on the volumes being replicated.
This was first published in December 2006