October 3, 2011

Teradata Unity and the idea of active-active data warehouse replication

Teradata is having its annual conference, Teradata Partners, at the same time as Oracle OpenWorld this week. That made it an easy decision for Teradata to preannounce its big news, Teradata Columnar and the rest of Teradata 14. But of course it held some stuff back, notably Teradata Unity, which is the name chosen for replication technology based on Teradata’s Xkoto acquisition.

The core mission of Teradata Unity is asynchronous, near-real-time replication across Teradata systems. The point of “asynchronous” is performance. The point of “near-real-time” is that it Teradata Unity can be used for high availability and disaster recovery, and further can be used to allow real work on HA and DR database copies. Teradata Unity works request-at-a-time, which limits performance somewhat;* Unity has a lock manager that makes sure updates are applied in the same order on all copies, in cases where locks are needed at all.

*Other options, more suitable for bulk loading and so on, are on the Teradata Unity roadmap.

The idea of doing real work on your high availability or disaster recovery database copies is an important one. Teradata systems are often used for the kinds of mission-critical purposes that call for such extra 2- or 3-way mirroring; so the ability to use all the systems for real work offers, if not exactly 2-3X price/performance savings, at least something significant. Teradata reports low but non-zero penetration in its customer base for active-active replication today. But I’m hopeful that number will increase, as Teradata Unity looks to be a big improvement over the possibilities that existed before.

In theory, the whole workload could be split among mirror-copy systems, although I’m sure we could construct various edge-case scenarios in which doing so would be a Bad Idea. In practice, I’d normally think of using second/third copies of a data warehouse for specific workloads, such as:

Another possibility to consider is only mirroring part of your database for HA or DR, since not all missions are equally critical. Yet another possibility is to mirror the whole thing, but on systems with different performance characteristics; in case of failover, you might only keep the most crucial applications up, while turning the others off until you can again run on a system powerful enough to handle them.

As Teradata tells it, Teradata Unity has two key aspects:

Further details may be seen in the slide deck Teradata graciously sent over for posting.

And finally, here’s some Teradata product name housekeeping:

Comments

One Response to “Teradata Unity and the idea of active-active data warehouse replication”

  1. Asis on October 4th, 2011 2:02 am

    Good info. While going through the Teradata’s slide deck it looks like in addition to Data Replication (Active-Active) they are keeping most used data kind of (In-Memory)Teradata Unity system. Good…

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