IT shops have more storage infrastructure choices than ever before as more vendors jump into the software-defined storage market.
Software-defined storage abstracts storage from hardware, making storage a pooled and fungible resource across physical boundaries, managed as a service according to policy. It isn't an entirely new concept -- storage virtualization has been around for years -- but putting the point of management control into the virtual server and consolidating storage and server resources onto one hardware platform is relatively novel.
An upcoming entrant into the software-defined storage market is VMware, which has made no bones about its desire to take over the management of data center networks and storage much like it did with servers. The company has several software-defined storage technologies on its 2013 roadmap, according to sources briefed on the company's plans, including vSAN, which is distributed software built into the ESXi hypervisor.
"Local disk can be much simpler than a SAN-based environment and [can] have higher performance, and as long as high-availability features like vMotion and HA continue to work, it's an attractive option," said Bob Plankers, a virtualization architect at a large Midwestern university.
VMware is far from the first to think of software-defined storage, and if its plans come to fruition, the company would enter a market where virtual storage appliances and software-defined storage offerings are already available.
Other companies that offer such products include Red Hat Inc., Oracle Corp.'s Sun, Nexenta Systems Inc., Hewlett-Packard's LeftHand, NetApp and EMC Corp. Recent newcomers to the market with software-defined storage designs specifically meant for virtualization include Nutanix, SimpliVity and Tintri.
Pros and cons of software-defined storage
IT pros see the potential benefits of software-defined storage and networking in virtual infrastructures. It could help the vision of private cloud computing come to life in the enterprise, said Kirk Bellmore, VMware systems engineer for a higher education institution in San Diego.
"This sets the stage for … [an environment where you can] run anywhere on any kind of platform at any time; spread it out or consolidate it," Bellmore said. "It just becomes like this elastic bubble of resources."
But there are elements that give IT pros pause. Rod Gabriel, IT infrastructure engineer at Wisconsin-based United Financial Services, said he would be cautious going down the road of integrating servers and storage.
"You have to feel comfortable with the technology," he said. "You also need to feel confident with regard to the vendor's long-term commitment to being a storage provider."
VMware software-defined storage design previews
VMware shared glimpses of its software-defined storage plans at VMworld last week. The three main features in the works, which VMware is publicly noncommittal about delivering, are vFlash, vSAN and vVols.
The vFlash feature creates a cached virtual layer to offload I/O from storage subsystems. It's based on VMware’s Content Based Read Cache, which caches the most-read blocks of data across virtual machines (VMs) in host memory.
VMware will pull Flash together as a resource pool, which allows for resource controls and shares to allocate Flash to apps, CTO Stephen Herrod said in a VMworld keynote. The vFlash feature is currently slated to be included in vSphere 5.5, sources said.
"With Fusion-io or [EMC's] Project Lightning, today you have to tell it, 'Go to this device,'" said a VMware pro familiar with the company's software-defined storage roadmap. "It's very manual. With vFlash, everything's built in, so any guest can take advantage of it."
The vSAN technology creates a converged storage-compute platform using direct-attached hard disk drives or solid-state drives on ESXi hosts, according to slides from a VMworld presentation. It will also include policy-based management, with per-VM settings for capacity, availability and IOPS. Users can create profiles, or policy-based management templates, as well.
The primary use cases for vSAN will be virtual desktop infrastructure, test and development, big data and disaster recovery, according to information from the VMworld session. As a property of the vSphere cluster object, the size of vSAN will only be limited by the current size of ESXi clusters, at 32 nodes, sources said.
"The advantage is, you have a whole cluster in a box: storage, networking and servers, and you're good to go," the VMware pro said.
The disadvantage will be for shops with blade servers, which can't hold much storage capacity yet.
Finally, vVols, which have been talked about for at least a year under various names, would change the main unit of storage management from a LUN to a VM object.
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