Hybrid clouds: a reminder for novice pilots

Hi, habrovchane! According to statistics , the cloud services market in Russia is constantly gaining momentum. More than ever in the trend of hybrid clouds - despite the fact that the technology itself is far from new. Many companies are thinking about how appropriate it is to maintain and maintain a huge iron park, including the situationally needed one, in the form of a private cloud.

Today we will talk about the situations in which the use of a hybrid cloud will be a reasonable step, and in which situations it can create problems. The article will be useful to those who previously did not have serious experience with hybrid clouds, but already looks at them and do not know where to start.
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At the end of the article we give a checklist of tricks that will help you when choosing a cloud provider and setting up a hybrid cloud.

All interested please go under the cat!

Private Cloud VS Public: Pros and Cons

To understand what causes business to move to a hybrid, let's look at the key features of public and private clouds. We will focus primarily on those aspects that in one way or another concern most companies. To avoid confusion in terminology, we give the following basic definitions:

A private (or private) cloud is an IT infrastructure, the components of which are located within one company and only on equipment owned by this company or cloud provider.

The public cloud is an IT-environment, the owner of which provides services on a chargeable basis and provides a place in the cloud for everyone.

A hybrid cloud consists of more than one private and more than one public cloud, the computational powers of which are shared.

Private clouds

At its high cost, a private cloud has several advantages that cannot be ignored. This is high manageability, data security, full monitoring of resources and equipment operation. Roughly speaking, a private cloud meets all the ideas of engineers about the ideal infrastructure. At any time, you can adjust the cloud architecture, change its properties and configuration.

No need to rely on external suppliers - all components of the infrastructure remain on your side.

But, despite the strong arguments for, a private cloud can be very expensive at the start and in the subsequent content. Already at the stage of designing a private cloud, it is necessary to correctly calculate the future load ... Saving at the start can lead to the fact that sooner or later you will encounter a lack of resources and the need for growth. And scaling a private cloud is a complicated and expensive process. Every time you have to buy new equipment, connect it and make adjustments, and this can often last for weeks - against almost instant scaling in a public cloud.

In addition to the cost of equipment, it is necessary to put financial resources on licenses and personnel.

In some cases, the balance of "price / quality", and more precisely, the "price of scaling and maintenance / benefits obtained" finally shifts towards prices.

Public clouds

If only you own a private cloud, then the public cloud belongs to an external provider that allows you to use your computing resources for a fee.

In this case, all that relates to the support and maintenance of the cloud, falls on the powerful "provider" shoulders. Your task is to choose the best tariff plan and make payment on time.

Using a public cloud for relatively small projects is much cheaper than maintaining its own fleet of equipment.

Accordingly, there is no need to maintain IT specialists and financial risks are reduced.

At any time you are free to change the cloud provider and move to a more suitable or more profitable place.

As for the minuses of public clouds, everything is quite expected: much less control by the client, lower performance when processing large amounts of data and low data security compared to private ones, which can be critical for some types of business.

Hybrid clouds

At the junction of the above advantages and disadvantages are hybrid clouds, which de facto are a bunch of at least one private cloud with one or more public. At first (and even at second) glance, it may seem that the hybrid cloud is a philosophical stone, allowing you to “inflate” the computing power at any time, make the necessary calculations and “blow away” everything back. Not a cloud, but David Blaine!



In fact, everything is almost as beautiful as in theory: a hybrid cloud saves time and money, has many standard and non-standard options for use ... but there are nuances. Here are the most important ones:

First of all , it is necessary to dock the “own” and “alien” cloud correctly, including in terms of performance. There can be a lot of problems here, especially if a data center with a public cloud is physically deleted or built on a different technology. In this case, there is a high risk of delays, sometimes critical.

Secondly , the use of a hybrid cloud as an infrastructure for a single application is fraught with uneven performance across all fronts (from CPU to disk subsystem) and reduced fault tolerance. Two servers with the same parameters, but located in different segments, will show different performance.

Third , do not forget about the hardware vulnerabilities of “alien” hardware (ardent greetings to Intel architects) and other security issues in the public part of the cloud, already mentioned above.

Fourth , the use of a hybrid cloud threatens a significant reduction in resiliency if it contains a single application.

Special bonus : now two clouds can “break” at once instead of one and / or a connection between them. And immediately in a variety of combinations.

We should also mention the problem of placing large applications in the hybrid cloud.
In the overwhelming majority of cases, it is impossible to just take and get in a public cloud, for example, 100 virtual machines with 128GB of RAM. More often than not, nobody will give you even 10 such cars.



Yes, public clouds - Moscow is not rubber. Many providers simply do not keep such a reserve of free capacity - and first of all it concerns the RAM. You can draw as many processor cores as you need, SSD or HDD volume - to issue several times more than is physically available. The provider will hope that you do not use the entire volume at once and it will be possible to increase it along the way. But if there is not enough RAM, the virtual machine or the application can easily collapse. And not always the virtualization system allows such tricks. In any case, it is worth remembering about such a development of events and discussing these moments with the provider “ashore”, otherwise you risk being left behind during peak loads (Black Friday, seasonal load, etc.).

So, if you want to use hybrid infrastructure, keep in mind that:

• The provider is not always ready to provide the necessary capacity on demand.
• There are problems and delays in connectedness of elements. You need to understand what pieces of infrastructure and in what cases will make requests through the “joint”, this can affect performance and availability. It is better to assume that there is not one cluster node in the cloud, but a separate and independent piece of infrastructure.
• There is a risk of problems in large parts of the landscape. In a hybrid solution, either one or the other cloud can completely fall off. In the case of a conventional virtualization cluster, you risk losing a maximum of one server, and here - immediately a lot and overnight.
• It is safest to treat the public part not as an “extender”, but as a separate cloud in a separate data center. True, in this case, you actually ignore the “hybridity” of the solution.

Smoothes the imperfections of the hybrid cloud

In fact, the picture is much more pleasant than you might have thought. The most important thing is to know the tricks of “cooking” a good hybrid cloud. Here are the main ones in the checklist format:

• You should not bring to the public cloud separately from the main software parts of the application that are sensitive to delays: for example, a cache or a database under OLTP load.
• Do not bring to the public cloud entirely those parts of the application, without which it will stop working. Otherwise, the probability of system failure will increase several times.
• When scaling, keep in mind that the performance of machines deployed in different parts of the cloud will be different. Scaling flexibility will also be far from perfect. Unfortunately, this is a problem of architecture design and you will not be able to completely eradicate it. You can only try to reduce its impact on the work.
• Try to ensure maximum physical proximity of the public and private clouds: the smaller the distance, the smaller the delays between segments. Ideally, both parts of the cloud “live” in the same data center.
• It is equally important to ensure that identical network technologies are used in both clouds. Ethernet-InfiniBand gateways can throw a lot of problems.
• If the same virtualization technology is used in private and public clouds, this is a definite plus. In some cases, you can negotiate with the provider about the migration of virtual machines as a whole without reinstalling.
• To benefit from the use of a hybrid cloud, choose a cloud provider with the most flexible charging options. Best of all - on actually used resources.
• Scale data centers: you need to increase capacity - we raise the “second data center” and set it under load. Finished the calculations? “Gasim” extra power and save.
• Separate applications and projects can be brought to the public cloud at the time of scaling private, or just for a period. However, in this case, you will not have hybridity, only the total L2 connectivity, which does not depend on the presence / absence of your cloud.

Instead of conclusion

That's all. We talked about the features of private and public clouds, considered the main possibilities for improving the performance and reliability of hybrid clouds. Nevertheless, the device of any cloud is the result of decisions, compromises and conventions dictated by business objectives and company resources.

Our goal is to motivate the reader to take seriously the choice of a suitable cloud infrastructure based on its own tasks, available technologies and financial capabilities.

We invite you to share your experience with hybrid clouds in the comments. Sure, your expertise will be useful to many novice pilots.