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Chapter 30. VDO Evaluation

30.1. Introduction

VDO is software that provides inline block-level deduplication, compression, and thin provisioning capabilities for primary storage. VDO installs within the Linux device mapper framework, where it takes ownership of existing physical block devices and remaps these to new, higher-level block devices with data-efficiency properties. Specifically, VDO can multiply the effective capacity of these devices by ten or more. These benefits require additional system resources, so it is therefore necessary to measure VDO's impact on system performance.
Storage vendors undoubtedly have existing in-house test plans and expertise that they use to evaluate new storage products. Since the VDO layer helps to identify deduplication and compression, different tests may be required. An effective test plan requires studying the VDO architecture and exploring these items:
  • VDO-specific configurable properties (performance tuning end-user applications)
  • Impact of being a native 4 KB block device
  • Response to access patterns and distributions of deduplication and compression
  • Performance in high-load environments (very important)
  • Analyze cost vs. capacity vs. performance, based on application
Failure to consider such factors up front has created situations that have invalidated certain tests and required customers to repeat testing and data collection efforts.

30.1.1. Expectations and Deliverables

This Evaluation Guide is meant to augment, not replace, a vendor's internal evaluation effort. With a modest investment of time, it will help evaluators produce an accurate assessment of VDO's integration into existing storage devices. This guide is designed to:
  • Help engineers identify configuration settings that elicit optimal responses from the test device
  • Provide an understanding of basic tuning parameters to help avoid product misconfigurations
  • Create a performance results portfolio as a reference to compare against "real" application results
  • Identify how different workloads affect performance and data efficiency
  • Expedite time-to-market with VDO implementations
The test results will help Red Hat engineers assist in understanding VDO's behavior when integrated into specific storage environments. OEMs will understand how to design their deduplication and compression capable devices, and also how their customers can tune their applications to best use those devices.
Be aware that the procedures in this document are designed to provide conditions under which VDO can be most realistically evaluated. Altering test procedures or parameters may invalidate results. Red Hat Sales Engineers are available to offer guidance when modifying test plans.