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Going All Flash, SAN-less and Staying Fault Tolerant

Benefitting from Flash Performance with Uninterrupted Service in a Virtualized Environment

Allon Cohen, PhD
Scott Harlin

Published May 2013


When server virtualization is added to an IT environment, application data is typically placed in a centrally reachable repository, such as a SAN, so that any application load can be run from any server in the data center through the use of virtual machines (VMs). Over the years, these external SAN repositories have been filled with hard disk drives (HDDs). Due to the fact that HDDs traditionally deliver between 200 and 350 input/output operations per second (IOPS) per drive, SAN’s had to include hundreds if not thousands of drives to keep up with the requirements of virtual server environments.

Figure 1
Figure 1: Concurrently running multiple virtual machines (VMs) in a virtualized environment will cause heavy randomization of data access towards the SAN

To complicate matters further, HDDs were designed primarily for handling sequential read and write data streams located on the same track. They cannot keep pace with randomized workload demands in virtualized environments as servers process concurrent data streams from multiple workloads that generate millions of IOPS. The resulting bandwidth from random read/ write storage requests create a system performance disparity in virtualized environments as external storage becomes the main bottleneck preventing servers from reaching their full potential. It is typical in today’s data center for thousands of VMs to compete for data from external storage arrays filled with slow HDDs that have trouble servicing this multitude of simultaneous requests. This bottleneck is depicted in Figure 1.

The solution in the past required IT departments to continue purchasing additional HDDs just to satisfy the server IOPS performance demands. As each SAN and its stockyard of HDDs continued to grow significantly more power and cooling was also required to keep the HDDs spinning, driving up data center total cost of ownership (TCO). As mechanical HDDs are prone to failure at random times, complex high availability (HA) schemes were also required to address individual HDD and storage array malfunctions. These schemes further increased the number of HDDs required to keep the system running and the HA software at the SAN layer resulted in higher CAPEX/OPEX costs to the data center.

In contrast, on-host flash memory storage, having no moving parts, handles random data access effortlessly making it a superior enabler of today’s virtualization requirements. A single flash-based SSD that fits directly into a server’s PCI Express (PCIe) bus can deliver random IOPS performance to VMs equivalent to large external SAN arrays deployed with thousands of HDDs. When flash is inside of the host, the solid-state technology becomes a local resource that is comparable to the IOPS performance requirements of servers and an excellent storage solution for a virtualized environment. However, deploying on-host flash in these environments requires care as choosing the wrong solution architecture results in negating critical virtualization services such as HA and Fault Tolerance (FT).

The purpose of this white paper is to present a deeper look at how OCZ Technology’s innovative virtualization solutions keep applications running at the speed of flash while at the same time provides uninterrupted services to end-users. Using these solutions and their ability to present flash as a highly available network resource sets the precedence for an all-silicon SAN-less data center that delivers all the benefits of virtualization without the need for costly back-end HDD SANs.

Table of Contents

  1. Introduction
  2. OCZ's On-Host Flash Solution
  3. Understanding Critical Services In a Virtualized Environment
  4. Enabling Uninterrupted FT Services to End-Users
  5. The SAN-Less Environment
  6. Conclusion
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