Solutions > High Availability > HVR versus Physical Block Replication

HVR Compared to Other Physical Block Replication Products

The High Availability provided by HVR differs from the high availability provided by products which replicate physical disk blocks to another machine. This table illustrates the differences;

HVR High Availability	Physical Disk Block Replication Products
HVR Disaster Recovery location may have different hardware, e.g. less CPUs or disks.	Disk-block level replication requires exactly the same hardware and software configurations within both the primary and secondary data centers.
HVR’s efficiency over a WAN means that it does not have any distance constraints between the primary and secondary data centers. This means that it’s affordable to put the Disaster Recovery in another town (not in same building) so it is not subject to the same power or network outages.	Disk-block level replication requires lots of network bandwidth because it transmits every database block i/o rather than only the compressed transaction data.
HVR provides additional protection for logical corruption, reducing the risk and business impact of human error which could lead to data corruption. In practice such ‘logical’ errors are more common and cause more downtime.	Disk-block level replication will ensure perfect copies of a damaged database.
With HVR the Disaster Recovery system is online, so you can see it is working.	A Disaster Recovery system fed by disk-block replication is offline until the disaster, so its functioning cannot be tested until after a disaster.
HVR is not restricted to one business need. The solution can simultaneously address multiple requirements inside the enterprise, such as Zero-downtime Maintenance, Zero-downtime Migrations, and a feed to a data warehouse for Realtime Business Intelligence.	Only for Disaster Recovery. A different solution would be needed to be purchased if the enterprise needed Realtime Business Intelligence.
Active/Active load balancing configurations for continuous availability.	No active/active. Disaster Recovery database must be offline at all times.
HVR allows off-load live reporting from the primary system, often reducing the size of system required to support the mixed workload.	No active/active. Disaster Recovery database must be offline at all times.
HVR can do file and database replication, so (for example) DBMS configuration files can be replicated to Disaster Recovery alongside the database changes.	Disk-block replication also replicates objects which are outside the database.