PROBLEM:
A major financial firm operated the largest message switch in the U.S., with hundreds of thousands of attached devices. It needed to comprise multiple HP NonStop Server nodes in an active/active configuration. These nodes were distributed around the U.S. for disaster tolerance.
SHADOWBASE SOLUTION - Homogeneous Active/Active Systems:
- The system supports true load-balancing by assigning each new request to the least heavily loaded node.
- Since the databases are kept in synchronization via asynchronous replication, data collisions occurs. But when the replication engines detect a collision, they resolve it automatically by using the data content of the updates to determine which update to accept and which to reject.
- For example, if the records have a time-stamp field indicating the time of the update, the replication engine can be directed to keep the most recent update and log the rejected update for later analysis, if desired. Otherwise the rejected update can simply be discarded. Other algorithms may also be used, such as choosing the highest or lowest value of a specified field, or choosing the earlier update, depending on the underlying applications need.
(Please click diagram to enlarge)
Please click here to contact us for more information on this Shadowbase solution.
The above was adapted from the book: Breaking the Availability Barrier, Volume III: Active/Active Systems in Practice by Paul J. Holenstein, Dr. Bruce Holenstein, and Dr. Bill Highleyman. Click here for more information on the book.