02 Jul 2013

Continuity and Cloud – Episode 4: Application Availability

In previous entries we examined using backup technologies and replication technologies, but what if your RPO and RTO are really, really tight? How do you get to near (or actual) real time recovery without a significant investment in hardware, communication links or replication software? In a typical business it’s usual to require fairly rapid recovery of the following business services:
  1. Identity and Security
  2. File and Print
  3. Email
  4. Commercial ERP System and its database
When you ask your business users, they generally want you to get these back as rapidly as possible, typically with very limited data loss.

How do I get a better result?

Fortunately there are a number of ways to achieve application resiliency for a limited cost and using a common set of tools. Almost all of these are available in your current operating systems and applications. When talking about Disaster Recovery and low RPO and RTO, I usually advise customers to have a small live footprint in our cloud. In this, run a minimal Active Directory Domain Controller. This provides you automatic replication in almost real time of all Identity and Security information. In the case of a disaster, you can rapidly take ownership of the FSMO roles and have all your current users and passwords synchronised. File and Print services can be similarly replicated through Microsoft Distributed File System (DFS-R). In Server 2008R2 and later, you can enable this service and connect it to a cloud based file server. As blocks are changed within files in your production file server, these are sent over the network and update the remote files server. Coupled with a live AD server, this provides you with almost instant availability of service for file systems. Later versions of Microsoft Exchange that support Distributed Availability Groups can likewise be enabled to provide you seamless fail-over of mail services to a small environment based in a cloud service like the Brennan IT cloud. Once set up, Microsoft Exchange can automatically replicate mail databases to the running cloud server. In case of failure services can be restored through standard Microsoft processes. ERP and Database workloads can utilise a separate running server in the cloud as an SQL Log target. This allows you to keep your database up to date in the cloud and enable a much faster restoration of your ERP services. In addition, utilising service provider licencing in the cloud can enable you to attach Business Intelligence or other reporting functions to this running server and increase the production capacity of your on-premise ERP. Achieving a rapid RPO and RTO can be cost effective. Utilising application resiliency is a very efficient way of restoring your business to operation quickly in the event of a catastrophic failure.
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