This content is part of the Essential Guide: VMware VSAN features and realities

VMware's VSAN 6: All-flash option, more snaps, no data reduction

VMware says VSAN 6 hyper-converged software will be released as part of vSphere 6, support all-flash nodes for better performance and scale to 64 nodes in a cluster.

VMware today said the next version of its Virtual SAN hyper-converged infrastructure software will support all-flash...

hardware and scale to 64 nodes per cluster.

Virtual SAN (VSAN) 6 (actually VSAN 2 but re-numbered to keep with the latest vSphere release) will be part of vSphere 6. VMware has not given a target ship data for vSphere 6 beyond saying it will launch in the first quarter of this year. VMware also confirmed that vSphere 6 will include support for long-awaited Virtual Volumes (VVOLS) to enable VM-aware storage in legacy arrays.

The first version of VSAN launched in early 2014. VSAN software pools storage resources such as hard disk drives, solid-state drives (SSDs) and PCI Express (PCIe) flash and makes them available to vSphere hosts in a cluster.

VSAN customers can either install the software on their VMware-certified hardware or on Ready Nodes sold by hardware vendors. They can also purchase EVO: RAIL systems from VMware partners with the software already installed.

VSAN 6 will not be available in EVO: RAIL configurations before the second half of 2015.

While the first version of VSAN was a hybrid setup using flash and hard disks, VSAN 6 can be used with only flash or as a hybrid. In a hybrid configuration, flash is used as a caching tier while persistent data goes to disk. The all-flash nodes have two tiers. The first tier can be PCIe or ULLtraDIMM flash and handles all initial writes. The second tier consists of SSDs. VSAN will support SSDs up to 4 TB.

VMware claims an all-flash VSAN can deliver more than four times the IOPS of an original VSAN, while a hybrid VSAN 6 is twice as fast as the previous version.

VMware also doubled the number of nodes that can be used in a cluster from 32 to 64. A 64-node cluster can scale to beyond 8 PB of storage capacity. VSAN 6 also supports 200 virtual machines (VMs) per host, doubling the number of the previous version.

VMware also added to VSAN file system technology from its 2013 Virsto acquisition. The Virsto file system provides up to 32 snapshots per VM (up from two), allowing 45 snaps per day.

VSAN 6 is also rack-aware -- it can place objects in nodes across multiple racks for fault tolerance. It also supports direct-attached JBODS, which enables it to run on blades.

VMware claims a maximum throughput of 90,000 IOPS per host and 7 million IOPS per cluster.

Still no dedupe, compression for VSAN

When VMware first launched VSAN, the vendor's executives admitted it was not yet ready for the enterprise. They considered it a storage option for use cases such as virtual desktop infrastructure and test/dev. But with VSAN 6, VMware now proclaims it is enterprise ready.

"With this release, we believe we can start to address business-critical applications," said Alberto Farronato, VMware director of product marketing for storage. "This platform is designed to be enterprise storage for the data center."

Unlike its main hyper-converged rivals Nutanix and SimpliVity, VMware still lacks data deduplication or compression in VSAN. Data reduction is something VSAN users have requested since the first version was in beta.

"Deduplication is not part of this release, but it's certainly part of our plans," Farronato said.

Another advantage most other hyper-converged products have over VMware is support for non-VMware hypervisors. VSAN is built into the vSphere kernel.

David Russell, Gartner distinguished analyst for storage, said VSAN will be compared closely to the early hyper-converged leaders Nutanix and SimpliVity. "VMware does not have feature parity across the board, but VSAN has enough capacity, scale and performance now that we will see greater adoption," he said. "We're seeing VSAN now come out of its nascent state to early mainstream or closer to full mainstream adoption."

Russell said customers may want even finer granularity than the 32 snaps per VM that VSAN 6 has, but the biggest missing piece is data reduction. "I expect the majority of the market wants data reduction," he said.

Along with dedupe and support for Microsoft Hyper-V, Nutanix also has an all-flash hyper-converged device.

VVOLs: A long-time coming

VVOLs, first previewed by VMware in 2011, allow storage vendors to add VM-enabled storage policies to their arrays. The goal is to enable storage provisioning without having to set up LUNs and NAS mount points. Vendors can also enable features such as deduplication, snapshots, replication and quality of service through VVOLs.

To use VVOLs, the storage hardware has to support the vStorage APIs for Storage Awareness. VMware said Dell EqualLogic, Fuijitsu Eternus, HP 3PAR StoreServ, Hitachi Data Systems NAS and VSP G1000, IBM XIV, and storage from Atlantis, CommVault, NexGen, Nimble Storage, Pure Storage and Tintri will support VVOLs in the first half of 2015. Vendors expected to add VVOL support later this year include DataCore, EMC, NEC, SimpliVity, SolidFire, Tegile, Veritas and Violin Memory.

"With VVOLs we introduce this integration framework that allows external storage arrays to understand the storage boundaries of VMs," Farronato said. "We call this VM-aware storage."

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