Every workload is going to demand cloud computing resources and services, which will pose a monthly expense to the business. It's important to understand the CPU, memory, disk and network I/O resources required by a mission-critical application, as well as how those resource demands will change over time.
Figuring out these numbers and cloud costs is usually accomplished by monitoring the mission-critical workload in-house during normal operations, and then correlating its performance to resources. The goal is to select a cloud instance or service type that offers adequate resources to meet the workload's peak requirements, but also minimizes the waste of idled resources.
For example, a large general-purpose Amazon Elastic Compute Cloud (EC2) instance with 2 vCPUs, 7.5 GB of memory and 32 GB of solid-state drive (SSD) storage space is priced at $0.14 per hour. But if there are situations when the workload might need more vCPUs, more memory or more storage, an extra-large EC2 instance with 4 vCPUs, 15 GB of memory and two 40 GB SSD disks may be required -- and that costs double, at $0.28 per hour.
Resource shortages can have a profound impact on workload performance, and they lead to larger resource allocations, which are costlier for the business. Part of your initial evaluation of a cloud provider should be to weigh the impact of resource shortages on mission-critical workload performance and understand the process and costs -- if any -- needed to change instances on demand or make other adjustments to resource allocations. For example, if it takes too long to change instances, or the larger instances become cost-prohibitive for the business, it may make sense to forego the cloud and leave the mission-critical workload in-house.
The most difficult workloads for cloud deployments are those with erratic, unpredictable or rapidly growing resource needs. Such workloads may be better accommodated in-house where the business can exert direct granular control over resource allocation to the virtual machine.
About the author:
Stephen J. Bigelow is the senior technology editor of the Data Center and Virtualization Media Group. He can be reached at firstname.lastname@example.org.
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