Understand the risks and costs of the public cloud

Companies have every interest in considering public cloud services. They make it possible to deploy virtual machines in a flexible way and at a lower cost, and to enhance the scalability and data backup capabilities of companies.

While it is important to understand the benefits of Iaas , it is also important to consider the critical disadvantages before engaging in project planning. This article examines purchase criteria and helps prepare for a tender.

Multi-tenant environment

One of the biggest drawbacks of the public cloud is its ability to be multi-tenant. The host server, on which your own VM runs, also hosts VMs from other companies. Because of this, public cloud providers do not give you access to the hypervisor. You can not install the tools at the host level, such as an anti-virus or backup agent. It also means that you can not associate a hypervisor with an existing domain or cluster. Consequences are also expected on the security side, as well as possible periods of service interruption caused by cloud or WAN failures.

In addition, public cloud providers own the hardware and control the underlying software layer. So they have the ability to make low-level changes, ad lib. Consider the amount of work required to schedule a server update. Normally, a company conducts a battery of intensive tests before updating the OS to ensure that there is no adverse effect. Conversely, if a public cloud provider can make low-level changes to the infrastructure without having to notify clients in advance, these changes can also impact client workloads.

Unpredictable costs

Another disadvantage to running your VMs in the cloud : the cost. It can indeed be very difficult to predict. Public Cloud Providers are not known to have simple billing templates.

Generally, billing is based on the amount of resources consumed. This includes storage, but also CPU, memory and I / O. Resource consumption can also be billed differently, at different times, and all activities at different levels. For example, some cloud providers make a difference between several CPU functions – and most importantly, bill them on a different scale.

Because, precisely, cloud provider billing formulas remain complicated, estimating the cost can be difficult. Depending on the intensity of use, the bill may vary from one month to the next. Fortunately, some vendors are providing portals to enable customers to control costs and implement contingency plans, stopping services when a certain (pre-defined) cost threshold has been reached.

The complexity of backups

Among other disadvantages, it is important to note that the public cloud can also complicate backup processes. If some of your VMs support critical workloads in the cloud , a backup is essential.

Although most cloud providers do their own backups, they do not necessarily offer recovery services. For example , you may need to perform VM backups yourself in your datacenter or on a backup server , which in turn are placed on another public cloud.

This may ultimately seem a little complicated; most backup tools support data backup to the cloud, but not from the cloud. A backup of data placed in the cloud increases the input / output consumption dedicated to the storage, the network or the bandwidth of the WAN. This results in increased costs.

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