Sometimes in life, you leave the party for five minutes and when you come back the conversation has changed. Everyone, it seems, is on the same page – but you feel out of the loop.

This is a sensation you might have experienced if you work in IT and hear people talking about containers and containerisation.

Containers have gone from zero to hero in the blink of an eye. Containerising apps – bundling them together with their files and libraries – is, everyone has suddenly agreed, far better than traditional VMs.

We're certainly not suggesting that containers are the emperor's new app deployment system. They have their advantages. But they're a relatively recent affair – and it's human nature to jump on the new and give it a tickle.

After all, this is an area of cloud technology that many VM developers are still wrapping their heads around – and these guys eat, sleep and breathe the cloud. They've probably got the cloud on speed dial.

So we're faced with a situation where the advantages of a new tech solution are being trumpeted at the expense of its disadvantages.

No one wants to be left behind – and when people talk about "modernising cloud environments" it must be good, right? Well, yes, but not always.

Before we take a look at some disadvantages of containerisation, let's clear something up. What, um, is it?

What are containers?

In a modernised cloud environment, cloud-native apps are kept in containers. In practice, this means that they're a kind of cloud-shaped chameleon. Whatever the device, a container is right at home.

It's like the international hand gesture for getting the bill in a restaurant. People know what you're asking for pretty much anywhere in the world.

A container is similar. Any Linux instance can run a container. Even Windows and Mac systems can run containers using a Linux virtual machine. They're neat, portable packages that are universally executable – and universally understood.

This makes deployment easy – at least in theory.

Their first main advantage is that they're lightweight. They run on the host machine's kernel rather than sitting atop the hardware they're virtualizing (as is the case with VMs).

And, yes, they're portable. They can be moved around without any changes being made to the underlying hardware or OS. It's like the difference between having an EU passport and having to fill out multiple visa forms.

So containers have their advantages. But they bring with them a host of drawbacks that may mean that your modernised cloud environment is paradoxically less dynamic than its predecessor.

One size doesn't fit all

The first issue with containers is that their very versatility can lead them to be deployed where they're not necessarily the best choice.

You don't need to replace every VM with an armada of containers – and anyway, some software just isn't suitable for containerisation.

There's a tendency in the cloud world to use the word "monolithic" to describe legacy apps. Monoliths are out-of-date and resistant to change. They lack dynamism and flexibility.

But maybe we shouldn't be thinking of legacy apps as monoliths but megaliths – traditional, yes, but also sturdy, durable and impressive. VMs aren't some creakingly inefficient Victorian contraption leaking steam and clanking away in the corner. In many cases, they work just fine.

Management issues

Cloud sprawl is a big problem for many organisations. Your manicured lawn can quickly turn into a chain of insect hotels.

Containers can contribute to this problem. Because they can be created, deployed and replaced at lightning speed, you can end up with far too many resources propping them up.

The truth is that they're often harder to manage than traditional, VM-based applications. Like a garden, they need continual pruning and cutting back. To successfully isolate them, you have to carry out fiddly network configurations. It takes time, money and persistence.

Container cheerleaders will tell you that there are container orchestration tools on the market like Kubernetes – but in reality, these can add complexity too.

Finally, there's a compatibility issue. Different formats aren't always compatible with each other, which can throw a spanner into your workloads.

Security

Hypervisor-based VMs can be easily isolated. Each bit of hardware is virtualised, so if one gets infected with a virus, it's effectively quarantined – it's not going to sneeze on another VM.

Containers, by contrast, share the same host kernel. This means a bad apple can spoil the bunch. A virus can be passed around other containers or even into the underlying OS.

Implementation

Even if something is beneficial in principle, you might find yourself bogged down by the process of implementation.

It's not only when they're installed that containers are tricky to manage. Introducing container networking to your cloud environment requires careful planning and management.

If you stint on preparation, you might end up with a dense thicket of containerised apps that are unable to properly communicate with each other or with external services.

Then there's the question of how your IT team will manage them. Their time and attention are probably already pretty stretched – do you really want to give them another plate to juggle?

So even if you're sold on the benefits of modernising your cloud environment with containers, you need to think long and hard about the process of implementation. Is there enough space in your diary and enough goodwill in your IT department?

The bottom line

Containers are far from useless. They're versatile, lightweight and portable, like a Swiss Army Knife or one of those beach towels you wear like a poncho.

But that doesn't mean that they're right for every job. Sometimes good old VMs are the better option.

There is, of course, the possibility of harnessing the best of both worlds. You can use VMware's vSphere while automating Kubernetes platform operations with VMware's Tanzu, to take one example.

Flexibility is one of cloud technology's greatest strengths. There doesn't have to be a "one-size-fits-all" solution to your problems. But it's worth bearing in mind that the answer to those problems isn't necessarily containerisation.

Ascend is a team of cloud computing experts based in Cork, Ireland. If you need assistance with a cloud migration or want to grow your cloud strategy, we're ready to help. Get in touch with one of our specialists for a free, no-obligation consultation.