Does software-defined storage stack up?

For most IT buyers, storage is a bit like air: it’s not important unless you’re running out.

But as data explodes and storage is sucked up, capacity is increasingly choked. Managing storage is suddenly very important and it’s a golden opportunity for storage resellers to provide a breath of fresh air.

Virtualised storage and solid-state media are now revitalising a field of computing that has consistently relied on the spinning disk since it abandoned tapes 30 years ago. Software-defined storage (SDS) is becoming especially important in a new world reliant on hybrid and private clouds, with scenarios demanding a mix of spinning disk and flash media.

But nothing in this industry is straightforward. Similar to software-defined networking, the precise definition of SDS varies according to each vendor’s interpretation.

To add to the confusion, storage is a hardware component that traditionally has had significant software control placed over it, with controllers such as file systems, data management and network-attached storage. It’s hard to know where SDS starts and ends.

Like other software-defined computing, SDS is heavily dependent on abstraction. Hiding the hardware under a layer of virtualisation is essential to SDS. Abstraction is what everyone agrees on.

The dispute comes in terms of defining what type of hardware should lie beneath the hypervisor.

According to Stephen Parker, head of cloud strategy at local aggregator Rhipe (formerly NewLease), the SDS world is generally divided into two sectors: the “closed ecosystems” that prefer specific hardware under the hypervisor, and the “open systems” that don’t favour specific brands.

The closed systems are dominated by the well-known brands such as Hewlett-Packard and EMC, while open systems include open-source vendors like Red Hat and proprietary but software-only players such as DataCore and VMware.

Parker warns that while many of the closed systems are tolerant of a variety of hardware, it’s an inevitability that the vendor’s own kit would run best on its software, which is not a criticism, just a natural consequence of knowing your own product better than others.

Parker points out that one approach is no less valid than the other.

“You have to ask what situation a reseller or a customer has currently,” says Parker. “If an environment already has a strong relationship and investment with a particular vendor, then it makes sense to continue with them and get the continuing support.”

The ‘purists’ of software-defined anything would say that the ultimate aim is to be hardware-agnostic – to the point of running commodity hardware in a virtualised pool. To this ideal, DataCore Software’s chief executive George Teixeira predicts that this year, servers will replace traditional storage arrays, with the help of SDS such as his company’s Virtual SAN product.

“Servers will combine with software-defined storage and continue to build momentum for a new class of ‘storage servers’ and hyper-converged virtual SANs,” says Teixeira. “The latest generation of servers is powerful and will continue to support large amounts of storage.

“Virtual SAN software is maturing rapidly and it will further drive the transformation of servers into powerful storage systems that go beyond today into full-blown enterprise-class virtual SANs.”

It’s not a surprising opinion from a software-only vendor, but others are sceptical about the role of commodity hardware in the space.

Distribution Central’s technical manager, Richard Denyer, reminds us there are kits from which you can build your own car. But he says very few people build their own vehicle for obvious time and reliability reasons. “You shell out for an already-assembled car because you know it works and you have support if anything goes wrong.”

In the same way, Denyer questions the value of resellers and customers spending time and effort to convert commodity hardware into storage.

“Data has gravity. Data is important. Do you want to go through the hassle of working out what hardware goes with what software? Even with the latest release of a software-defined storage product – and I’ll pick on VMware’s vSAN as an example – not every piece of hardware works well with vSAN,” says Denyer.

“The internet [highlights] people complaining about how ‘hardware X’ doesn’t work with vSAN. As a customer do you want to go through that? You can buy a server and purchase whatever SDS product and go through the process of making it all work. But what happens when something goes wrong? Who do you ring?

“Storage is important. Commodity storage is the same as kit cars – not everyone’s a mechanic,” says Denyer.

Melbourne systems integrator Perfekt deals with all the major storage vendors. Senior integration specialist Cristian Danci agrees the channel should focus on abstraction when thinking about software-defined storage, and get their minds off commodity hardware.

“Even if you use commodity hardware, the software is still proprietary. That’s a critical dist-inction [to make],” says Danci.

“We’ve found a whole bunch of [storage] customers where they’ve said, ‘Just give us the software and we’ll go and build the hardware’. But then a lot of them come back and say, ‘The hardware is too hard to do, please give us the hardware’.”

“Even though it’s just commodity hardware, the engineering teams still need to determine what processor should be used, what RAM should be used, what interoperability it needs, how it will best perform under specific configurations...That’s really, really hard to do.

“That’s why the vendor’s own storage hardware still works the best, because their engineering teams have done all the work in actually getting the hardware to work, which is a really hard process to do.”

Danci also points out that the commodity market moves very rapidly, and it’s difficult for even the most diligent SDS vendor to keep up with making their software fit the nuances of every new box.

When the industry was first turned onto the potential of SDS, the role of commodity hardware was poorly understood, says Adrian De Luca, chief technology officer of Hitachi Data Systems Asia-Pacific.

“A couple of years ago there was a misconception of reduced cost resulting from using commodity hardware with software-defined networking,” he says.

“Now it’s all about agility – the ability to scale out and call for additional services at will.”

In defence of commodity hardware’s potential in SDS, Westcon’s manager of innovation and services, Darryl Grauman, says there are “self-healing” storage utilities now emerging. Such tools will make commodity hardware more reliable, but he warns that until this nascent field of technology matures it is best to stick with specialist-storage hardware underneath a software-defined storage system.

Next: Why bother with SDS?