Recently on the blog, with articles regarding thin clients like the secure viewer, it’s important that the issue of Redundancy also be addressed. Any time your application is critical or you are using thin clients, it’s important to have redundancy in place. To ensure your operations continue to run smoothly, you need some form of redundancy. Here are a few of the terms related to redundancy, and what they mean for SCADA software users.
RAID – Redundant Array of Independent Disks. This is a term for replication and storage of data on multiple disk drives. Numbers after the acronym RAID will help determine the schemes and architectures of the data. The operating system will read the RAID array as one disk, despite the fact that it is registered across many. This increases data reliability and input/output performance. In some RAID configurations, a whole hard drive may go bad, but can be replaced with a new one, and the system will recreate the data on the replacement drive without missing a beat.
Data Redundancy – Data redundancy means only that the same data is stored in multiple locations, or that the data can be extrapolated from other data. Data redundancy is particularly important in SCADA software, because there are circumstances in which a loss of data is not acceptable; for example, in a pharmaceutical application that is 21 CFR Part 11 compliant, or when an environmental scrubber is burning off toxins and data is required to be available for EPA reporting.
Store and Forward – Store and Forward is often used in SCADA software, database connections. For example when data is sent to an external database as the primary location, a secondary (local) database would be set up as “store and forward”. If the connection to the primary (remote) database was disconnected for a period of time, the data would be logged to the secondary database until the primary came back online. Then the stored data would be forwarded (or synchronized) with the primary without any data being lost.