VMware VSAN features and realities
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SAN FRANCISCO -- Early beta testers of VMware Inc.'s Virtual SAN said it could change the way their companies provision...
and manage storage, and that they see the product as a potentially viable alternative to hyper-converged storage systems.
VMware launched the beta program of its Virtual SAN (vSAN) this week at VMworld. The vSAN clusters hard drive and flash storage capacity from ESXi hosts and uses the pool for virtual machine (VM) placement.
One session at the conference included a panel of administrators from large companies that participated in the vSAN private beta. These users gave vSAN high grades for simplicity and convenience, but requested more storage management features. While vSAN is unlikely to replace large storage area networks (SANs) in their companies, they said, it could be valuable for uses such as virtual desktop infrastructure (VDI) storage and remote offices.
The beta users compared vSAN to hyper-converged storage systems from startups Nutanix, Pivot3, Scale Computing and SimpliVity. "It's similar to the Nutanix model," said Travis Goodfellow, senior principal IT technologist at medical device manufacturer Medtronic, based in Minneapolis. "What I like about vSAN most is the tight integration not only in the kernel, but in vCenter. It's also flexible. I can provision hardware whenever I want it. For more storage-heavy needs, I can use more storage in the unit. For more memory-heavy requests, I put more memory in the unit."
Mike Han, IT Infrastructure Manager at Best Buy in Richfield, Minn., said the hyper-converged vendors "are small, and we don't know if they're going to be around tomorrow. That's one of the challenges they have," he said. "At the same time, we looked at Nutanix and they have a nice product."
“VSAN and Nutanix look a little different,” added Mike Wilson, cloud systems architect at Minnetonka, Minn.-based online payment company Digital River. “Choosing Nutanix forces you to buy hardware again. With vSAN, we can just run it on what we have. We already own stuff and want to run vSAN on it."
Medtronic's Goodfellow said the hyper-converged platforms are still missing networking built into the stack. "Nutanix is great for the storage stack and the compute stack, but it doesn't include anything from the network stack," he said. "It can plug into the network just fine, but it's another thing you have to manage."
Comparing vSAN to other hyper-converged storage systems, James Streit, virtualization architect at New York-based international media company Thomson Reuters, said: "One key difference is that vSAN's VMs are built into the kernel; it's not a VM running on each host providing storage."
VSAN rated flexible and simple; Where's the dedupe?
Among the beta testers, vSAN won points for being easy to set up and manage, and for its policy-based storage profiles.
"I was surprised I could take a node and configure it a bunch of ways," said Dominic Rivera, assistant vice president (VP) of virtual infrastructure at U.S. Bank. "It could automatically claim a node or I can claim it myself. Most of us aren't storage administrators by trade, and this made it simple for us to provision storage for our VMware environment."
"It doesn't take a rocket scientist to set this up," Best Buy’s Han added.
On the downside, several testers said they would like to see features such as deduplication and snapshots built in. VSAN is useless with diskless servers, and there were questions from the audience in the session about how high it will scale.
VMware Product Manager Kiran Madnani said vSAN is designed to support 32-node clusters, but the vendor has only tested eight nodes for the beta. He said each node can have 36 disks.
While the beta users have only used vSAN for testing, several said they see obvious use cases for the product.
"I think there will still be a need for a monolithic storage array," Medtronic's Goodfellow said. "There are things that vSAN doesn't have today that will be put in that will compete with a monolithic array, but they aren't there today. There will be use cases where it will be ideal -- like VDI or Web servers that are stateless."
Han said vSAN is a good fit "in remote locations where it doesn't make sense to bring up a SAN. Some [administrators] might have a lot of those locations -- I have quite a few -- where they have high disk requirements but don't have local [storage] expertise."
Who's responsible for the storage?
Whenever VMware adds a storage product or feature, it raises the issue of how storage provisioning duties will be divided among virtualization administrators and storage admins. VSAN is no exception.
"This will put more responsibility on the virtual team and away from the storage teams," Thomson Reuters' Streit said. "Do teams have the extra cycles for that?"
U.S. Bank's Rivera said he thought systems like vSAN could bring storage teams closer to their server counterparts. "VSAN makes it inevitable that storage and compute teams that are separate today will converge," he said.
Hyper-converged vendors react
Executives from several hyper-converged vendors said they are not concerned about vSAN, at least not immediately. Hyper-converged vendors are relatively new to the market, but they already have systems running in production and include some of the more advanced features vSAN still lacks. SimpliVity has had deduplication built in since it started shipping OmniCube, and Nutanix recently added dedupe for flash and memory tiers.
"The vSAN is two or three years away from being ready," said SimpliVity CEO Doron Kempel. "And then they have to add dedupe. So we have about a six-year lead. After that, maybe we have to switch to KVM [kernel-based virtual machine] hypervisors."
Vanessa Alvarez, VP of marketing at Indianapolis-based Scale Computing, said vSAN will have more of an impact on competitors because the other systems use VMware hypervisors, while Scale's HC3 uses KVM.
"We use KVM because we don't pass on the cost of VMware licensing," she said. "But if you are going to use a VMware hypervisor, wouldn't you just use vSAN instead of somebody else's system?"