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Controlling Costs in the Cloud for High-Availability Applications

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One of the more useful cost containment tools involves the tagging of resources. Tags consist of key/value pairs and metadata associated with individual resources, and some can be quite granular. For example, each virtual machine, along with the CPU, memory, I/O, and other billable resources it uses, might have a tag. Other useful tags might show which applications are in a production versus development environment, or to which cost center or department each is assigned. Collectively, these tags could constitute the total utilization of resources reflected in the bill.

Organizations that make extensive use of public cloud services might also be well-served to create a script for loading information from all available monitoring, management, and tagging tools into a spreadsheet or similar application for detailed analyses and other uses, such as chargeback, compliance, and trending/budgeting. Ideally, information from all CSPs and the private cloud would be normalized for inclusion in a holistic view to enable optimizing price/performance for all applications running throughout the hybrid cloud.

Handling the Worst-Case Use Case: High-Availability Applications

In addition to the reasons cited in the introduction for why high-availability applications are often the most costly, all three major CSPs—Google, Microsoft, and Amazon—have at least some high availability-related limitations. Examples include failovers normally being triggered only by zone outages and not by many other common failures; master instances only being able to create a single failover replica; and the use of event logs to replicate data, which creates a “replication lag” that can result in temporary outages during a failover.

None of these limitations is insurmountable, of course—with a sufficiently large budget. The challenge is finding a common and cost-effective solution for implementing high-availability across public, private, and hybrid clouds. Among the most versatile and affordable of such solutions is the storage area network (SAN)-less failover cluster. These high-availability solutions are implemented entirely in software that is purpose-built to create, as implied by the name, a shared-nothing cluster of servers and storage with automatic failover across the local area network and/or WAN to assure high availability at the application level. Most of these solutions provide a combination of real-time block-level data replication, continuous application monitoring, and configurable failover/failback recovery policies.

Some of the more robust SAN-less failover clusters also offer advanced capabilities, such as WAN optimization to maximize performance and minimize bandwidth utilization, robust support for the less-expensive Standard Edition of SQL Server, manual switchover of primary and secondary server assignments for planned maintenance, and the ability to perform routine backups without disruption to the applications.

Maintaining the Proper Perspective

While trying out some of these suggestions in your hybrid cloud, endeavor to keep the monthly CSP bill in its proper perspective. With the public cloud, all costs appear on a single invoice. By contrast, the total cost to operate a private cloud is rarely presented in such a complete, consolidated fashion. And if it were, that total cost might also cause sticker shock. A useful exercise, therefore, might be to understand the all-in cost of operating the private cloud—taking nothing for granted—as if it were a standalone business such as that of a cloud service provider. Then those bills from the CSP for your mission-critical applications might not seem so shocking after all. 

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