Tapping servers to scale out storage

VMware extends the software-defined concept to enterprise storage, touting its Virtual SAN offering as a new way of using servers to provide storage services.
Written by Eileen Yu, Senior Contributing Editor

SAN FRANCISCO — In an ideal environment, an organization's storage and compute experience should be completely converged as one resource pool, encompassing the necessary capabilities such as provisioning and performance monitoring. 

VMware believes this can be delivered via a software-based storage model running on server clusters. 

The virtualization vendor today announced a slew of product releases here this week at its annual tradeshow VMworld. Among these is the beta release of Virtual SAN (VSAN), which it says extends the concept around software-defined network to the storage realm. 

In a blog post Monday, VMware's chief strategist Chuck Hollis pointed to the need for storage to be a "dynamic, programmable resource" operating much in the same way as a virtualized server environment.

To this end, the vendor's VSAN offering showcases a software-based storage array that carries out its duties by tapping server clusters and unused capacities in direct-attached storage, he said. Essentially, the same server farm is used to deliver both compute and storage services, Hollis added. 

In an interview with ZDNet, John Gilmartin, VMware's vice president of cloud infrastructure, explained that each server typically has its own local SSDs (solid-state drives) and hard drives. These can be pooled together to create a virtual, distributed storage system, running on virtual machines (VMs) each governed by individual sets of policies.  

"What makes it more interesting is the idea of policy-based management. Traditionally with storage, you have to create WANs which have big pool capacities and have very specific capabilities. With VSAN, you can define policies at the VM level," Gilmartin noted.

For instance, it can comprise a VM that is not very important and does not need protection, as well as another VM that has higher availability requirements and need to withstand two hardware failures. "You can drop both VMs on the same data store and we can implement the required policy on per-VM basis," he explained, adding that this can be further administered around the necessary storage capabilities and performance.


This essentially means businesses can deploy a new tier of shared storage system from their existing server pool, Gilmartin said. 

Noting that VSAN is deployed as an extension to VMware's vSphere virtualization platform, Hollis said this presents a delivery model that tightly integrates storage and compute resources. 

"The idea of carving multiple storage service levels from available resources isn't a new idea. Doing so dynamically at the time of provisioning, without having to pre-allocate and pre-configure the pools...is," he said.

According to Hollis, each VSAN cluster can comprise between three and eight server nodes, each of which must have at least one SSD and SAS disk drive. Each server can support up to five disk groups and up to seven hard disks. 

Licensed on a per-CPU pricing model, VSAN is currently in beta and is slated for general public release in the first half of 2014.

Eileen Yu of ZDNet Asia reported from VMworld 2013 in San Francisco on the invitation of VMware. 

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