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Always On Applications with IBM HyperSwap Solution
May 25, 2021 | Written by: Deepak Yadav
Categorized: . | IT infrastructure
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Today we shall all agree to one common expectation that our applications should remain accessible at all times round the clock.
At the same time, unpredictability in natural disasters for example earthquake, cyclone, tornado leads to potential disruption of many essential services.
There’s a saying ‘Disasters cannot be totally prevented but their impact can be reduced’. This needs a lot of planning referred to as a disaster recovery plan and high availability plan.
While both disaster recovery and high availability sound similar there is a crisp difference between them:
- Disaster Recovery tends to demonstrate the ability to resume application at some point after a specific disaster and needs specific fail over task with associated RPO and RTO.
- High availability is the ability to have continuous access to application during and after a specific disaster with an effective RPO an RTO of zero.
(RPO: Recovery point objective is the maximum acceptable amount of data loss measured in time and zero RPO articulates to no data loss.
RTO: Recovery time objective is the maximum acceptable time to bring the business up and running after a disaster)
IBM has been a front runner in helping its clients achieve Disaster recovery and high availability with its Spectrum software suite. Today, I am sharing my thoughts on one specific architecture of high availability called ‘HyperSwap’ for continuous availability of data.
The IBM HyperSwap function is a high availability feature that provides dual-site, active-active access to data during planned and unplanned outages.
HyperSwap function ensures it has one data copy at local site(local storage) and another data copy at another site(remote storage). Data that is written by the application is automatically sent to both data copies. If one site is no longer available, the other site can provide access to the data seamlessly with no manual intervention required.
To construct HyperSwap volumes, active-active relationships are made between the copies at each site. These relationships automatically run and switch directions according to which copy or copies are online and up to date.
(Volumes: Identifiable fixed unit of data storage)
The relationships provide access to whichever copy is up to date through a single volume, which has a unique ID. Relationships can be grouped into consistency groups just like Metro Mirror and Global Mirror relationships. The consistency groups fail over consistently as a group based on the state of all copies in the group. An image that can be used for disaster recovery is maintained at each site.
The Small Computer System Interface (SCSI) protocol allows storage devices to indicate the preferred ports for hosts to use when they submit I/O requests. Using the Asymmetric Logical Unit Access (ALUA) state for a volume, a storage controller can inform the host of which paths are active and which ones are preferred.
In a HyperSwap self-healing system, the function behaves as below:
- During normal operations, the system suggests that the application host use local storage over remote storage based on observed latency.
- During local storage system failure, the system suggests the application host to use remote storage by using the alive set of data paths without any change/manual admin intervention.
- During a complete site disaster, the system provides continuous access of data from remote storage to clustered application instance on the other site ensuring a seamless transition of data access.
Clients with these stringent availability requirements surely will benefit from proven a HyperSwap solution that requires no additional software or hardware based on IBM Spectrum Virtualize software making the whole solution SIMPLE.
Disclaimer: The postings on this site are my own and don’t necessarily represent my organizations positions, strategies, or opinions.
Connect with IBM SMEs on LinkedIn: Deepak Yadav
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