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QLC flash storage: What it costs and its best use cases

QLC flash brings high capacities at costs coming down close to spinning disk. So what are the use cases for QLC solid state, which make best use of its relatively low endurance

We are truly entering the flash era. Four or five years ago, the market for flash storage was arguably still emerging, but since then solid state has become the norm.

Discussion is now not about whether, but what type of flash to deploy. We’ve seen flash technology evolve too, from single and multi-level cell (SLC, MLC) flash via TLC (triple-level cell) – all of which indicate the number of charges a flash cell operates with – and now we are seeing quad-level cell (QLC) flash storage that can store four bits per cell.

What is QLC flash, what does it cost and what use cases is it good for?

In the past year or so, we’ve really started to see QLC technology take off and become more widely accepted.

Part of the reason for that has been the steady reduction in price. Research organisation Wikibon has been tracking how QLC prices compare to those of HDD systems and it’s clear there’s been a significant narrowing between the two.

Last December Wikibon indicated the way that prices were shifting. HDD suppliers may disagree their technology is stuttering but Wikibon believes, in terms of capacity, flash has already overtaken hard drive sales and that this is an accelerating trend, with much of that take-up being of QLC technology.

The company regularly publishes figures that show the gap between HDD and SSD prices. These show an average HDD price of $45 per TB in 2015, compared to a flash price of $840. Currently, the prices are $21 and $86 respectively but in 2026, the two are projected to be identical, with each TB costing $15.

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But there needs to be some context put on those figures. When it comes to QLC specifically, however, it’s harder to get a handle on prices. Suppliers offer list prices – which may not have much reflection on what’s really going on – and there’s a vast spread of prices according to supplier, the way they’re deployed, and the quality of the products.

As an example, last year Nimbus launched a 64TB QLC flash drive for £8,000. That works out at about £125 per TB.  But prices can go a lot higher depending on performance. Pure Storage has dived into the fray by announcing a QLC version of its all-flash array. This comes in at about $500 per TB but you’re getting more than just drives for that.

QLC flash use cases

It’s not just the fall in prices that has prompted greater take-up of QLC flash. There are many factors that drive the need for QLC but there’s an underlying explanation for all of them. That is, the need to manage and analyse data at ever faster speeds. You can add to this the growing use of IoT devices and emerging technologies such as driverless cars, which will both benefit from the faster read times offered by QLC.

There are many applications in today’s tech environment that suit QLC’s strengths of being able to support reading data and analysing it quickly. The growing importance of analytics is a testament to the recognition that businesses need to do more with customer data.

There are a couple of additional areas where QLCs have been having an impact. One of them is in virtual environments such as VMware and Hyper-V implementations. The ability of this technology to allow policy-based provisioning is an element that fits in well with QLC’s strengths.

But there are other areas too. The faster speeds of QLC can help organisations improve the way that they handle data protection, for example in the way that companies restore snapshots.                                                                                                                      

Finally, the growth of cyber attacks is having an immediate effect on IT departmental budgets, in particular the growing frequency of ransomware demands.  We’re going to see more QLC being used to speed up the restoration of the last dataset after such attacks.

While it seems there is plenty of scope for QLC within the enterprise, it’s not going to be suitable for everything. As with all existing flash storage technologies, there are limitations on the number of rewrites possible. QLC is great for read-only applications but there are limitations for enterprise use because of this.

QLC devices will suffer greater wear too and, thus, will have a shorter lifecycle. So, any implementations that require longevity should be avoided.  

On-site versus off-site

There’s clearly been a greater trend towards cloud deployment and the use of QLC mirrors that trend.

One aspect of this is that companies now want to consume storage in a different way and turn to a pay-as-you-go model.

Gartner research backs this up. The company found that by 2025, at least 50% of enterprises will shift toward Opex-based storage consumption models. This compares to the current figure of fewer than 10%.

Furthermore, the research company found that by 2023 exactly one fifth of companies will use management tools to integrate storage platforms directly with public cloud. QLC deployments in backup and restore will be a big part of this.

There’s also the very real factor that behind the cloud, users aren’t going to know what’s being used; they consume services, not technology. But one factor that will drive cloud providers is that need to preserve space, while maintaining performance. And that’s where QLC will play a part in future deployments.

QLC: Set to have impact despite limitations

It is clear that QLC technology is set to have a big impact in the future. It’s been a technology that’s been simmering under the surface for some time but it’s needed the more recent price falls to become more widely accepted. It’s going to be a widely used flash technology for some years to come. Penta-level cell (PLC) flash is in the pipeline for the coming years but that’s still a fair way away.

But tech managers do need to be aware of the barriers of QLC; it is a harder tech to make work in enterprise, those over-writing limitations will serve as a handicap for some organisations.

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