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Feature - 4 March 2021 (ComputerWeekly)

Hyper-converged infrastructure: Why software-defined everything might not work for all datacentres

Choosing the right converged infrastructure in the first instance can mean trading off security and agility requirements.

While all datacentres have become in essence defined by their software, going for a fully fledged, software-defined hyper-converged infrastructure (HCI) will not always be the right course for every operator.

Not all need maximum abstraction and, for those that do, there can be critical barriers to achieving a true HCI-based environment.

Ross Warnock, director at datacentre infrastructure provider and consultancy EfficiencyIT, says the essential trade-off to consider is likely to be between security and agility.

However, datacentre operators should kick off the decision-making process by ensuring they have the difference between converged and hyper-converged infrastructures clear, he suggests.

Suppliers use the terms to mean different things – typically leaning towards the specific context in which the supplier in question operates.

“There is a lot of misinformation out there,” says Warnock. “Converged and hyper-converged are similar and share the same goal.

“Converged infrastructure is primarily designed to simplify the deployment of compute networking and storage resources. Hyper-converged has the same goal but a slightly different approach, in the sense that hyper-converged infrastructure is with software-defined compute – and typically on commodity components.”

Some operators may want to maintain a portion of their storage fabric, while others will not want to have “all their eggs in one basket”, he says.

Operators should ask how much flexibility in design and equipment they need, and consider their overall security requirement on top of that.

For many companies, that primary HCI goal of easing management by having a single control pane is unattractive, says Warnock. It represents a potential vector for an attack which, if successful, could give the perpetrators access to anywhere and everything.

“And that is not necessarily a flaw in the product,” he says. “So that’s probably the main difficulty.”

There are several reasons not to go for maximum abstraction, including the question of in-house skillsets.

Traditional approach

Warnock says the traditional approach of having a team that includes one person focused on storage, another in charge of networking, another for applications and yet another on the application layer will partly cancel out the benefits of an HCI migration.

“You need someone who understands all those elements well enough,” says Warnock. “With the skills that are in it, that can be difficult. If you speak to a storage specialist, generally, their networking knowledge is very limited. So to get someone at that level who is an expert in all those fields is difficult.”

After all, a key HCI driver is about looking to manage the whole shebang via a single pane of glass when a migration is complete, he adds. Also, can you take the team with you? HCI migrations are complex, even stressful. Close examination of all assets and requirements is essential and even when done right, remediation will be required, simply because it is a move to a new environment.

“In some cases, there will be quite a lot of remediation; in others, things will be quite simple,” says Warnock. “Sometimes it can’t be done, so you physically cannot move.”

He doubts that a “lift and shift” migration in one bite would be feasible in many cases, except perhaps in a very small environment with relatively “loose” requirements – maybe a startup with everything virtualised, rather than a lot of applications that will struggle in a hyper-converged environment.

“In reality, you see so many legacy applications that people are still running from years gone by that they are just trying to hold on to,” he says. “There is always something there.”

Organisations need to confirm first why they want HCI, he says. If it is to reduce costs via easier management, those hoped-for savings can be years away. A company needs to be in a position where it can afford to put those years in and come out the other side.

Instead, companies doing HCI are often looking to speed up application deployment, says Warnock.

Weighing up the costs

According to supplier Nutanix, in its HCI business case guide, operators must be sure they are comparing apples with apples when estimating total cost of migration. Traditional storage area network (SAN) and all-flash arrays have their own migration requirements and costs ...


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