Welcome!

Virtualization Authors: Roger Strukhoff, Elizabeth White, Carmen Gonzalez, Victoria Livschitz, Pat Romanski

Related Topics: Virtualization, .NET, Open Source, Cloud Expo, Security, SDN Journal

Virtualization: Article

Can You Trust VDI Storage Benchmarks?

The truth behind VDI benchmarks

by George Crump, Storage Switzerland

VDI (Virtual Desktop Infrastructure) implementation projects are going to be priorities for many IT Managers in 2013 and a key concern will be end-user acceptance. If the users don't embrace their virtual desktops they won't use them and the project is doomed to failure. The key to acceptance is to provide users with an environment that feels the same, performs better and is more reliable than their current stand-alone system. The storage system bears most of the responsibility in delivering that experience.

IT managers who want to capitalize on the opportunity that the virtual desktop environment can focus on two key capabilities when they evaluate storage system vendors. The first is being able to deliver the raw performance that the virtual desktop architecture needs and the second is doing so in the most cost effective way possible. These are two capabilities that are traditionally at odds with each other and not always well-reflected in benchmark testing.

For most organizations the number-one priority for gaining user acceptance is to keep the virtual desktop experience as similar to the physical desktop as possible. Typically, this will mean using persistent desktops, a VDI implementation in which each user's desktop is a stand-alone element in the virtual environment for which they can customize settings and add their own applications just like they could on their physical desktop.

The problem with persistent desktops is that a unique image is created for each desktop or user, which can add up to thousands of images for larger VDI populations. Obviously, allocating storage for thousands of virtual desktops is a high price to pay for maintaining a positive user experience.

In an effort to reduce the amount of storage required for all of these images, virtualized environments have incorporate features such as thin provisioning and linked clones. The goal is to have the storage system deliver a VDI environment that's built from just a few thinly provisioned ‘golden' VDI images, which are then cloned for each user.

As users customize their clones, only the differences between the golden image and the users' VDIs need to be stored. The result is a significant reduction in the total amount of storage required, lowering its overall cost. Also, the small number of golden images allows for much of the VDI read traffic to be served from a flash-based tier or cache.

When a write occurs from a thinly provisioned, cloned virtual desktop more has to happen then just the operation to write that data object. The volume needs to have additional space allocated to it (one write operation), the metadata table that tracks unique branches of the cloned volume has to be updated (another write operation) and some sort of parity data needs to be written, depending on the RAID protection in place. Then, finally, the data object is written. This entire process has to happen with each data change no matter how small.

Herein lays the tradeoff in using these features. While reducing the amount of space required for the VDI images, thin provisioning and cloning increase the demand for high write performance in the storage system. This presents a significant opportunity for storage system vendors who can address these new performance requirements.

Many storage systems that use a mix of flash memory and hard disk technology don't use the higher performing flash for writes; they use it for actively reading data. While these storage systems have storage controllers designed to handle high read loads, the increased write activity generated by thin provisioning and cloning is still going to relatively slow hard disk drives. Because this type of I/O traffic is highly random, the hard drives are constantly "thrashing about". Basically the controller sits idle while it waits for the hard disk to rotate into position to complete each write command. Even systems with an SSD tier or cache may have problems providing adequate performance because they too don't leverage the high speed flash for write traffic.

Due to the high level of thin provisioning and cloning, plus the fact that once a desktop is created a large part of its I/O is write traffic, many cached or tiered systems do not perform well in real-world VDI environments and can provide misleading VDI Benchmark scores.

The Truth Behind VDI Benchmarks
Most VDI Benchmarks focus primarily on one aspect of the VDI experience, the time it takes to boot a given number of virtual desktops. The problem with using a "boot storm test" is that this important but read-heavy event is only a part of the overall VDI storage challenge. During most of the day desktops are writing data, not reading it. In addition, simple activities such as logging out and application updates are very write-intensive. The capability of a storage system to handle these write activities is not measured by many VDI benchmarking routines.

A second problem with many VDI benchmarking claims is that for their testing configuration they do not use thinly provisioned and cloned volumes. Instead, they use thick volumes in order to show maximum VDI performance.

As discussed above, in order to keep user adoption high and costs low most VDI implementations would preferentially use persistent desktops with thin provisioning and cloning. Be wary of vendors claiming a single device can support over 1000 VDI users. These claims are usually based on the amount of storage that a typical VDI user might need as opposed to the Read/Write IOPS performance they will most likely need.

Trustworthy VDI Performance
A successful VDI project is one that gains end-user acceptance while reducing desktop support costs. The cost of a storage system that can provide thin provisioning, cloning and an adequate sized flash storage area to support the virtual environment could be too high for some enterprises to afford.  And, an additional cost could be incurred with the performance problems that are likely to appear after the initial desktop boot is completed because of the high level of write I/O.

The simplest solution may be to deploy a solid state appliance like Astute Networks ViSX for VDI. These devices are 100% solid state storage to provide high performance on both reads AND writes. This means that boot performance is excellent and performance throughout the day is maintained as well.

With a solid state based solution to the above problems, performance will not be an issue, but cost may still be. Even though it can provide consistent read/write performance throughout the day for a given number of virtual desktops, the cost per desktop of a flash based solution can be significantly higher than a hard drive based system.

However, it's likely in larger VDI environments (400+ users) that flash-based systems are really the only viable alternative to meet the performance requirements which can easily exceed 100 IOPS per user. Fortunately, flash-based systems can also produce efficiencies that bring down that cost in addition to the well-known benefits of using 1/10th the floor space, power and cooling compared to traditional storage systems.

First, the density of virtual desktops per host can be significantly higher with a flash appliance. And, the system is unaffected by the increase in random I/O as the density of virtual machines increases.

Second, the speed of the storage device compensates for the increased demands of thin provisioning and cloning operations run on the hypervisor. These data reduction services can now be used without a performance penalty. This means that the cost of a storage system with a more powerful storage controller and expensive data services like thin provisioning and cloning can be avoided.

Finally, the flash appliance is designed to tap into more of the full potential of solid state-based storage. For example, Astute uses a unique DataPump Engine protocol processor that's designed to specifically accelerate data onto and off of the network and through the appliance to the fast flash storage. This lowers the cost per IOPS compared to other flash-based storage systems.

Most legacy storage systems use traditional networking components and get nowhere near the full potential of flash. In short, the appliance can deliver better performance with the same amount of flash memory space. This leads to further increases in virtual machine density and space efficiency because more clones can be made - resulting in very low cost per VDI user.

Conclusion

VDI benchmark data can be useful but the test itself must be analyzed. Users should look for tests that not only focus on boot performance but also performance throughout the day, and at the end of the day. If systems with a mix of flash and HDD are used then enough flash must be purchased to avoid a cache miss, since these systems rarely have enough disk spindles to provide adequate secondary performance.

A simpler and better performing solution may be to use a solid state appliance like those available from Astute Networks. These allow for consistent, high performance throughout the day at a cost per IOPS that hybrid and traditional storage vendors can't match. Their enablement of the built-in hypervisor capabilities, like thin provisioning, cloning and snapshots, also means that they can be deployed very cost effectively.

>

George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments.

More Stories By Derek Kol

Derek Kol is a technology specialist focused on SMB and enterprise IT innovations.

@ThingsExpo Stories
The 3rd International Internet of @ThingsExpo, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that its Call for Papers is now open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than 20 years ago.
Cultural, regulatory, environmental, political and economic (CREPE) conditions over the past decade are creating cross-industry solution spaces that require processes and technologies from both the Internet of Things (IoT), and Data Management and Analytics (DMA). These solution spaces are evolving into Sensor Analytics Ecosystems (SAE) that represent significant new opportunities for organizations of all types. Public Utilities throughout the world, providing electricity, natural gas and water, are pursuing SmartGrid initiatives that represent one of the more mature examples of SAE. We have s...
The security devil is always in the details of the attack: the ones you've endured, the ones you prepare yourself to fend off, and the ones that, you fear, will catch you completely unaware and defenseless. The Internet of Things (IoT) is nothing if not an endless proliferation of details. It's the vision of a world in which continuous Internet connectivity and addressability is embedded into a growing range of human artifacts, into the natural world, and even into our smartphones, appliances, and physical persons. In the IoT vision, every new "thing" - sensor, actuator, data source, data con...
The Internet of Things is tied together with a thin strand that is known as time. Coincidentally, at the core of nearly all data analytics is a timestamp. When working with time series data there are a few core principles that everyone should consider, especially across datasets where time is the common boundary. In his session at Internet of @ThingsExpo, Jim Scott, Director of Enterprise Strategy & Architecture at MapR Technologies, discussed single-value, geo-spatial, and log time series data. By focusing on enterprise applications and the data center, he will use OpenTSDB as an example t...
How do APIs and IoT relate? The answer is not as simple as merely adding an API on top of a dumb device, but rather about understanding the architectural patterns for implementing an IoT fabric. There are typically two or three trends: Exposing the device to a management framework Exposing that management framework to a business centric logic Exposing that business layer and data to end users. This last trend is the IoT stack, which involves a new shift in the separation of what stuff happens, where data lives and where the interface lies. For instance, it's a mix of architectural styles ...
An entirely new security model is needed for the Internet of Things, or is it? Can we save some old and tested controls for this new and different environment? In his session at @ThingsExpo, New York's at the Javits Center, Davi Ottenheimer, EMC Senior Director of Trust, reviewed hands-on lessons with IoT devices and reveal a new risk balance you might not expect. Davi Ottenheimer, EMC Senior Director of Trust, has more than nineteen years' experience managing global security operations and assessments, including a decade of leading incident response and digital forensics. He is co-author of t...
The Internet of Things will greatly expand the opportunities for data collection and new business models driven off of that data. In her session at @ThingsExpo, Esmeralda Swartz, CMO of MetraTech, discussed how for this to be effective you not only need to have infrastructure and operational models capable of utilizing this new phenomenon, but increasingly service providers will need to convince a skeptical public to participate. Get ready to show them the money!
The Internet of Things will put IT to its ultimate test by creating infinite new opportunities to digitize products and services, generate and analyze new data to improve customer satisfaction, and discover new ways to gain a competitive advantage across nearly every industry. In order to help corporate business units to capitalize on the rapidly evolving IoT opportunities, IT must stand up to a new set of challenges. In his session at @ThingsExpo, Jeff Kaplan, Managing Director of THINKstrategies, will examine why IT must finally fulfill its role in support of its SBUs or face a new round of...
One of the biggest challenges when developing connected devices is identifying user value and delivering it through successful user experiences. In his session at Internet of @ThingsExpo, Mike Kuniavsky, Principal Scientist, Innovation Services at PARC, described an IoT-specific approach to user experience design that combines approaches from interaction design, industrial design and service design to create experiences that go beyond simple connected gadgets to create lasting, multi-device experiences grounded in people's real needs and desires.
Enthusiasm for the Internet of Things has reached an all-time high. In 2013 alone, venture capitalists spent more than $1 billion dollars investing in the IoT space. With "smart" appliances and devices, IoT covers wearable smart devices, cloud services to hardware companies. Nest, a Google company, detects temperatures inside homes and automatically adjusts it by tracking its user's habit. These technologies are quickly developing and with it come challenges such as bridging infrastructure gaps, abiding by privacy concerns and making the concept a reality. These challenges can't be addressed w...
The Domain Name Service (DNS) is one of the most important components in networking infrastructure, enabling users and services to access applications by translating URLs (names) into IP addresses (numbers). Because every icon and URL and all embedded content on a website requires a DNS lookup loading complex sites necessitates hundreds of DNS queries. In addition, as more internet-enabled ‘Things' get connected, people will rely on DNS to name and find their fridges, toasters and toilets. According to a recent IDG Research Services Survey this rate of traffic will only grow. What's driving t...
Scott Jenson leads a project called The Physical Web within the Chrome team at Google. Project members are working to take the scalability and openness of the web and use it to talk to the exponentially exploding range of smart devices. Nearly every company today working on the IoT comes up with the same basic solution: use my server and you'll be fine. But if we really believe there will be trillions of these devices, that just can't scale. We need a system that is open a scalable and by using the URL as a basic building block, we open this up and get the same resilience that the web enjoys.
Connected devices and the Internet of Things are getting significant momentum in 2014. In his session at Internet of @ThingsExpo, Jim Hunter, Chief Scientist & Technology Evangelist at Greenwave Systems, examined three key elements that together will drive mass adoption of the IoT before the end of 2015. The first element is the recent advent of robust open source protocols (like AllJoyn and WebRTC) that facilitate M2M communication. The second is broad availability of flexible, cost-effective storage designed to handle the massive surge in back-end data in a world where timely analytics is e...
We are reaching the end of the beginning with WebRTC, and real systems using this technology have begun to appear. One challenge that faces every WebRTC deployment (in some form or another) is identity management. For example, if you have an existing service – possibly built on a variety of different PaaS/SaaS offerings – and you want to add real-time communications you are faced with a challenge relating to user management, authentication, authorization, and validation. Service providers will want to use their existing identities, but these will have credentials already that are (hopefully) i...
"Matrix is an ambitious open standard and implementation that's set up to break down the fragmentation problems that exist in IP messaging and VoIP communication," explained John Woolf, Technical Evangelist at Matrix, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
P2P RTC will impact the landscape of communications, shifting from traditional telephony style communications models to OTT (Over-The-Top) cloud assisted & PaaS (Platform as a Service) communication services. The P2P shift will impact many areas of our lives, from mobile communication, human interactive web services, RTC and telephony infrastructure, user federation, security and privacy implications, business costs, and scalability. In his session at @ThingsExpo, Robin Raymond, Chief Architect at Hookflash, will walk through the shifting landscape of traditional telephone and voice services ...
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at Internet of @ThingsExpo, James Kirkland, Chief Architect for the Internet of Things and Intelligent Systems at Red Hat, described how to revolutioniz...
Bit6 today issued a challenge to the technology community implementing Web Real Time Communication (WebRTC). To leap beyond WebRTC’s significant limitations and fully leverage its underlying value to accelerate innovation, application developers need to consider the entire communications ecosystem.
The definition of IoT is not new, in fact it’s been around for over a decade. What has changed is the public's awareness that the technology we use on a daily basis has caught up on the vision of an always on, always connected world. If you look into the details of what comprises the IoT, you’ll see that it includes everything from cloud computing, Big Data analytics, “Things,” Web communication, applications, network, storage, etc. It is essentially including everything connected online from hardware to software, or as we like to say, it’s an Internet of many different things. The difference ...
Cloud Expo 2014 TV commercials will feature @ThingsExpo, which was launched in June, 2014 at New York City's Javits Center as the largest 'Internet of Things' event in the world.