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Gravic turns up the temperature on synchronous replication

Gravic bringing Sizzling-Hot-Takeover support for synchronous replication to the NonStop marketplace.




Let’s talk about something that is hot, really hot! Sizzling hot! From the time Gravic first began talking about Sizzling-Hot-Takeover (SZT) Replication Systems it caught our attention. In presentations given by Gravic it is hard to miss the presence of SZT, occupying a place between Active / Passive and Active / Active replication, and for good reason. Now you can configure your Disaster / Recovery (DR) environment to have some of the benefits of what Active / Active configurations provide without embracing a full-blown Active / Active configuration. Turns out, running applications on the passive system is no longer out of the question.


Gravic Shadowbase (feb17)


Gravic today supports three architectures for Shadowbase; Active / Passive replication, the Sizzling-Hot-Takeover replication and the Active / Active replication, as per graphic above. With as much talk as there is these days about the merits of Active / Active replication, there are many reasons why this simply isn’t an option.

For some customers it’s the cost of the additional licenses required while for others it may be that their applications and perhaps their networks are not set up to support the separation of data as may be appropriate for Active / Active replication. SZT supports the applications running in parallel on the Active and Passive systems, such that a failure of the Active system can be rectified by a switch to the Passive system that has the application up and running.

Most outages aren’t catastrophic. Perhaps the first instincts of operations staff are to persist with running a “hobbled” Active system as they work around the issues fueling the outage. This is oftentimes an instinct driven by a deep reluctance to “throw the switch” out of fear there will be application or network issues when trying to failover to the passive system. Unless regular switching between Active and Passive systems is built into the daily or weekly routines of operations, in times of crisis there is a deep seeded fear that any transfer of online transactions to the Passive system may only further exacerbate the situation.

The architecture of Sizzling-Hot-Takeover mitigates these anxieties and at price points much less than what it would be for more aggressive Active / Active configurations. For all three architectures supported by Gravic, there are two distinct technologies in support of them – asynchronous communications, as well as the latest addition from Gravic, synchronous communications. SZT is supported today with asynchronous communications.

When SZT is supported by synchronous communications – an important option that Gravic expects to make available to the NonStop community later this year – not only can the cut over between systems be instantaneous but there will be no loss of committed data even when a disaster takes out the Active system. When combined with synchronous communications, Synchronous SZT has applications that are already up and running and there’s no loss of data – the switch can now be thrown with less fear of the unknown.

While it is recommended to always include regular switching between the Active and Passive systems in order to better familiarize operations with the processes involved, attention can now be directed to monitoring other aspects of the transition. As for the health of the applications running on the Passive system, “test transactions” can be routinely sent to the Passive system at any time just to add to the confidence of the operations staff should a catastrophe develop.

Best practices are always a key element of any DR plans. There’s still no lessening in the need to stick with plans to move transactions between systems to ensure the network can correctly redirect the traffic. But when the Sizzling-Hot-Takeover architecture supports a synchronous communications technology, Gravic will then provide the NonStop community with zero data loss options when it comes to deploying the most appropriate DR solution for the budget on hand.


If you would like to know more about Sizzling-Hot-Takeover, then please feel free to contact Gravic management at