In-Depth

Breaking Down VMware VSAN 6.0

How does the new, all-flash version compare with VSAN 5.5?

More vSphere 6.0 coverage:

VMware Inc. announced a raft of new products Monday, and one of the key ones was VSAN 6.0. The company put a unique spin on VSAN, and is differentiating it from other software-defined storage (SDS) solutions by categorizing it as "software-defined storage delivered via the hypervisor." By doing this, the company seems to be positioning its solution as unique from the other SDS offerings, as well as capitalizing on the unique placement of VSAN in the hypervisor's software stack and its intimate knowledge of the vSphere virtual environment.

Less than a year ago, VMware first released VSAN. The company now claims to have more than 1,000 customers. With the second release of VSAN, it's shooting for performance and capacity gains.

All-Flash VSAN
The biggest performance gain will be from being able to configure an all-flash VSAN. With the previous version -- VSAN 5.5 -- VMware certified only spinning disks for persistent storage; SSDs were for caching. VSAN 6.0 overcomes that limitation, as SSDs can now be used for persistent storage, as well as caching.

VMware claims that the all-flash VSAN of v6.0 will provide a consistently high level of performance and extend VSAN use cases to applications that require low latency (sub-millisecond latencies) and a high IOP count (up to 100,000 IOPS per host). VMware also says you can host 200 virtual machines (VMs) per all-flash VSAN host. Interestingly, and understandably, an all-flash VSAN array only uses the cache for writes.

All-New File System
VSAN 5.5 was based on a modified version of VMware Virtual Machine File System (VMFS); VSAN 6.0 gets its own file system, cleverly called VSAN file system. This new file system supports "instant clones" and more efficient snapshots. The new file system also is touted as being twice as performant as VSAN 5.5 when used in hybrid mode. VMware has increased the recommended VM count per VSAN host by 50 percent, from 100 to 150.

VSAN 6.0 now supports direct-attached hard disk arrays. This will be a boon to blade systems that had limited usefulness in a VSAN 5.5 cluster, because they only supported one or two direct-attached storage devices.

Petabytes of Storage
As VSAN is a feature of vSphere, it now supports 64 hosts per VSAN cluster. In theory, although a 64-node VSAN cluster could support 14PB of storage (64nodes * 35 disks * 6TB), it's unlikely that such a system would be very performant or even supported by VMware. But it is an interesting possibility.

With a year of customer use and more than 1,000 customers, VMware is now confident enough in VSAN that it's recommending it for Tier-1 and business-critical applications. Interestingly, the company split the naming of VSAN into Virtual SAN 6 All-Flash and Virtual SAN 6.0 Hybrid, but have yet to announce pricing and packaging. Could it use this differentiator to waterfall the hybrid product down into one of the versions of vSphere?

About the Author

Tom Fenton works in VMware's Education department as a Senior Course Developer. He has a wealth of hands-on IT experience gained over the past 20 years in a variety of technologies, with the past 10 years focused on virtualization and storage. Before re-joining VMware, Tom was a Senior Validation Engineer with The Taneja Group, were he headed their Validation Service Lab and was instrumental in starting up its vSphere Virtual Volumes practice. He's on Twitter @vDoppler.

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