Choosing Storage Devices for VMware All Flash Virtual SAN (Without Overspending) — Part 1

By Joe Cook - 2015-11-23

This is the first post in a new blog series focused on expanding the possibilities and capabilities of virtualization through flash technology.

"Flash technology has fundamentally changed the paradigm of storage systems and is enabling new use cases for essential enterprise applications and solutions by enhancing their performance, efficiency, and design."
~ Sandeep Dutta, Country Manager, Storage, IBM India/South Asia.

The Case for Flash

Storage workload needs are evolving at an unprecedented rate. Workloads that were once satiated by the IOPS of spinning disks (HDDs) now greedily hunger for the performance flash-based devices (SSDs) offer. In all aspects of the data center, more and more HDDs are being replaced with reliable, efficient, low-cost SSDs. With flash costs coming down to the same as or below that of HDDs, the demand for flash deployment in data centers of all sizes is skyrocketing.

To meet increased workload service level agreements (SLAs), new storage array technologies are being created around flash devices. VMware's All Flash Virtual SAN is one such technology and is at the forefront of the storage evolution. VMware's All Flash Virtual SAN offers increased value by virtualizing the local flash storage resources of ESXi hosts, then grouping these resources into tiers of storage dedicated to caching and capacity and presenting them to the consumer as a single auto-managed datastore.

With the introduction of VMware VSAN 6.1, VSAN includes support for flash devices in both caching and capacity tiers. This means virtual machine workloads are no longer held hostage by slow-spinning HDDs. Instead, by leveraging flash-based storage devices in the capacity tier, the bottleneck inherent in traditional storage is removed and storage performance is unleashed.

Also new in version 6.1, VMware All Flash Virtual SAN includes increased support for flash device interfaces. With the inclusion of NVDIMM and NVMe, support is now offered for all five major interfaces of persistent flash storage devices:  NVDIMM, NVMe, PCIe, SATA, and SAS.

Selecting the Right SSD for VSAN

With the cornucopia of choices for flash-based devices, how do we choose the right mix of characteristics to meet the I/O needs of the general enterprise workload? What are the key factors to look for in choosing a flash-based device or SSD that will meet the majority of general enterprise workload needs without overspending? Is selection based on speed, endurance, cost, or manageability?

As with most things in life, too little or too much of one thing is typically not the best approach:

  • Too little performance for the solution results in needing to scale sooner than necessary.
  • Too much performance for workload needs results in unnecessary spending.
  • Too little endurance shortens the lifespan of the drive and accelerates the device refresh cycle.

No single quality can independently dictate a viable candidate for a flash-based storage device. It is not the fastest of devices that is the most viable, nor is it the one with the lowest cost. It is the one most balanced in all qualities—performance, availability, capacity, and economics—relative to the workload being considered. It is the synergy between each aspect that provides the real value in your solution.

Maximizing the synergistic value of your storage solution does not mean you have to maximize the cost. Over-engineering of storage solutions should be a trend of the past. Do not let your choice of storage devices unnecessarily increase your overall solution TCO. Design to avoid overspending. You do not have to overbuy. Buy what you need. Buy balanced. Buy synergy.

This article starts a series where we will explore how to choose storage devices for use in VMware Virtual SAN. In coming blog posts, we will offer guidance around best practices in choosing flash devices for the capacity and caching tiers of VMware's All Flash Virtual SAN.

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Joe Cook