Unidesk VDI Management Software Solves the VDI Capacity Problem . .... requirements, particularly IOPS, and account for
Dell Desktop Virtualization Solutions (DVS) Technical Report
Overcoming the Storage Challenges of Persistent Virtual Desktops with Dell EqualLogic Hybrid Arrays and Unidesk
ABSTRACT The ability of Dell™ EqualLogic hybrid arrays to automatically tier data between SSD and SAS makes these hybrid arrays a very cost-effective option for meeting the persistent virtual desktop requirements for IOPS, as well as for disk space requirements when used in conjunction with Unidesk® VDI management software. This technical report provides a proof point for how Unidesk desktop layering technology and Dell EqualLogic hybrid arrays combine to increase user density and reduce storage cost per user, based on testing performed in Dell Desktop Virtualization Solutions (DVS) Labs.
Copyright © 2012 Dell Inc. All Rights Reserved. Dell EqualLogic is a trademark of Dell Inc. All trademarks and registered trademarks mentioned herein are the property of their respective owners. Possession, use, or copying of the documentation or the software described in this publication is authorized only under the license agreement specified herein. Dell, Inc. will not be held liable for technical or editorial errors or omissions contained herein. The information in this document is subject to change.
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PREFACE Dell Desktop Virtualization Solutions (DVS) Enterprise Infrastructure Overview: DVS Enterprise Infrastructure is designed and optimized to deliver a highly robust, highly scalable and highly available enterprise solution designed for implementations in sophisticated IT environments. The DVS Enterprise infrastructure implements enterprise scale virtualized servers, multi-tier virtual SAN storage and robust enterprise network architecture for multiple demanding use cases requiring enterprise scaling, redundancy, high density, and sophisticated management of all system components. It has been designed to scale from 50 to 50,000 users. Dell EqualLogic Overview: Dell EqualLogic PS Series arrays are intelligent storage arrays that are designed to provide simple management and seamless expansion using innovative Dell Fluid Data™ technology. All PS Series storage arrays include SAN configuration features and capabilities that sense network connections, automatically build RAID sets, and conduct system health checks to help ensure that all components are fully functional. EqualLogic PS Series arrays are based on a virtualized modular storage architecture that enables IT managers to purchase only the storage they need—when they need it—to help prevent both underutilization and over-provisioning. Using innovative Fluid Data technology, all EqualLogic PS Series arrays in a SAN work together to automatically manage data, load balance across all resources, and expand to meet growing storage needs. Unidesk VDI Management Software Unidesk, a strategic Dell partner, is offered by Dell as a validated virtual desktop management option for Dell Desktop Virtualization Solutions (DVS) Enterprise Infrastructure and DVS Virtual Labs. By replacing block-based cloning, image management, application virtualization, and profile management point tools with a more complete, unified solution, Unidesk makes it easier for IT organizations to package and deliver applications, and create, patch, and support fully personalized desktops hosted on VMware vSphere®. Unidesk’s patent-pending desktop layering technology integrates with Citrix® XenDesktop®, VMware View™, and other brokering solutions to enable enterprises to expand VDI to more users, reduce desktop operations costs up and cutting VDI storage capacity upwards of 70%.
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TABLE OF CONTENTS PREFACE ....................................................................................................................................................... iii TABLE OF CONTENTS.................................................................................................................................... iv Executive Summary....................................................................................................................................... 1 Key Findings .................................................................................................................................................. 2 Introduction .................................................................................................................................................. 3 The Challenges of Persistent Virtual Desktops ............................................................................................. 4 Storage Capacity Requirements for VDI ....................................................................................................... 4 Storage IOPS Requirements for VDI.............................................................................................................. 5 Dell EqualLogic Hybrid Arrays Solve the VDI IOPS Problem.......................................................................... 5 Unidesk VDI Management Software Solves the VDI Capacity Problem ....................................................... 6 More Benefits of Combining Dell Hybrid Arrays with Unidesk ..................................................................... 7 Test Configuration and Tools ........................................................................................................................ 8 Testing Method ............................................................................................................................................. 9 Storage Analysis and Results....................................................................................................................... 10 Storage Performance Analysis .................................................................................................................... 11 Conclusion: Combining Dell EqualLogic Hybrid Arrays with Unidesk Maximizes IOPS and Minimizes Capacity When Deploying a Dell DVS Enterprise Infrastructure Solution .................................................. 12
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Executive Summary Dell’s Desktop Virtualization Solutions (DVS) offer a full portfolio of end-to-end solutions that are designed to help a wide range of IT organizations implement virtual desktop infrastructures- from the device to the datacenter to the cloud. DVS is designed to ease design and implementation complexities and address each organization’s unique business, user, and IT requirements. By accelerating adoption of desktop virtualization, organizations can adapt to the dynamics of today’s more mobile and global workforce and take advantage of the consumerization of IT, while enhancing security, IT flexibility, and business continuity. The innovative DVS approach integrates purpose-built hardware, software, and services to deliver innovative and flexible end user computing solutions to customers via a single sourceDell. One of the biggest barriers to widespread desktop virtualization adoption has been storage. Implementing virtual desktops at any scale quickly becomes cost-prohibitive if you thick-provision every desktop with a full-sized disk image. Image sharing and de-duplication technologies can reduce the amount of required storage capacity and provide higher levels of cache hits and reusable blocks, but the sheer magnitude of desktop IO, the higher percentage of write IO compared to read IO, and the random, “bursty” IO patterns of desktop workloads force administrators to add spindles back, offsetting capacity savings. Because of these challenges, many early adopters have seen their VDI projects stall or fail. They either exhaust their capital budgets paying too much for storage, or they do not take into account the IO requirements of their desktop use cases, resulting in an unacceptable user experience. It is therefore critical for those planning and implementing VDI to understand both storage capacity and performance requirements, particularly IOPS, and account for both with the equipment and software solutions they select. It is also critical to understand use cases. Implementing non-persistent desktops that use cloning technology to reduce the storage footprint may satisfy task workers who will accept a desktop that is basically the same as everyone else’s. Knowledge workers, however, typically require a persistent desktop that gives them a modern, customizable experience. Unidesk, a strategic Dell partner for DVS management, helps solve the use case, storage, and management challenges with its desktop layering technology. Unidesk creates persistent desktops on the same small storage footprint that cloned image technology can only use for non-persistent desktops. Because the desktops are persistent, they sustain all user changes, including user-installed applications, making knowledge workers happy. Unidesk also offers simpler, more robust image management and application delivery capabilities than the combination of provisioning, application virtualization, and profile management tools. The Dell DVS group recently conducted a series of tests using Unidesk in a VMware View™ deployment to quantify the storage benefits of desktop layering.
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The test results confirm that the combination of Dell™ EqualLogic™ hybrid arrays and Unidesk are exceptionally well-suited for VDI environments, and provide an ideal capacity/performance balance that offers unparalleled user density. Specifically, Dell EqualLogic hybrid SAN arrays enhance the performance and efficiency of VDI deployments by combining SSD and SAS drives within a single chassis. The EqualLogic firmware provides automatic tiering and balancing of stored data between the SSD and SAS tiers to provide more IOPS at less cost. Unidesk desktop layering technology enables the Dell EqualLogic hybrid arrays to deliver the same IO performance on less than half the capacity footprint of standard persistent virtual desktops. Unidesk persistent virtual desktops share the same operating system and application layers, reducing the storage footprint upwards of 70% compared to full desktop clones, and providing storage savings similar to non-persistent shared image technologies. Unidesk desktops creates an optimal data pattern that effectively exploits the automated tiering of Dell EqualLogic hybrid arrays, such that hot blocks are stored on SSD, and less frequently accessed data is migrated to SAS. The result is more IOPS delivered on a smaller storage footprint for greater user density –and much lower storage cost/user.
Key Findings Our testing showed remarkable synergy between Unidesk VDI management software and Dell EqualLogic hybrid storage arrays for overcoming VDI capacity, IOPS, and cost challenges. Unidesk desktop layering technology shares a single layer of the Operating System (OS) and common applications such as Microsoft Office across many virtual desktops to significantly reduce VDI capacity requirements. This same sharing of OS and application layers makes it easy for Dell EqualLogic hybrid arrays to identify hot blocks, and store the commonly accessed OS and application files on its faster SSD drives. The result is extremely low latency for both read and write operations, enabling you to host many more virtual desktops on a single array and still deliver enough IOPS to provide a high performance user experience. The increased user density makes Dell EqualLogic hybrid arrays a much more cost-effective solution for VDI than all-SSD arrays or standard SAN arrays. Compared to providing an identical user experience with thick-provisioned full clones,, the increased desktop density provided by Unidesk significantly reduces storage deployment costs, as shown in the following chart depicting Dell EqualLogic PS Series hybrid arrays in both deployment scenarios.
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Unidesk reduces storage capacity by over 70% 12 10
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# of XVS arrays
Disk capacity (TB)
25
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# of virtual desktops Full Clone
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Figure 1 – Comparison of How Many Dell EqualLogic PS6010XVS Arrays are required to Host Virtual Desktops With and Without Unidesk VDI Management Software As the remainder of this white paper will show, combining Unidesk with Dell EqualLogic hybrid arrays maximizes array performance to solve the VDI IOPS problem, and reduces the storage footprint upwards of 70% to increase user density greater than 3x compared to full clones on Dell EqualLogic hybrid arrays.
Introduction Striking the right balance between storage capacity, IOPS, and cost is one of the most difficult challenges when implementing Virtual Desktop Infrastructure (VDI). The use of traditional SAN storage typically requires capacity to be over-provisioned to meet the IOPS requirements of virtual desktop workloads. The use of high-cost, low-latency solid state drives (SSDs) can deliver sufficient IOPS on a smaller storage footprint, but capacity ends up being under-provisioned, and the cost to add more SSD quickly becomes prohibitive. Dell EqualLogic PS Series hybrid arrays and Unidesk VDI management software combine to provide an optimal balance between storage capacity, IOPS, and cost for organizations that require persistent desktops capable of sustaining all user customizations. During the development of this paper, Dell DVS performed a significant amount of testing using Dell hardware, VMware vSphere and VMware View, and Unidesk VDI management software. We found that Unidesk desktop layering technology provisioned virtual desktops on VMware vSphere that used up to 3
70% less storage compared to thick-provisioned persistent desktops, significantly increasing user density on the Dell EqualLogic hybrid array. The array was able to deliver more than enough IOPS on this smaller storage footprint to provide a high-performance user experience, resulting in a much lower storage cost per user compared to traditional SAN storage.
Figure 2 – The Simple VDI “Stack” Enabled by the Combination of Dell EqualLogic Hybrid Arrays, Dell PowerEdge Servers, VMware, and Unidesk
The Challenges of Persistent Virtual Desktops When persistent virtual desktops are required to meet the desktop customization needs of knowledge workers, many organizations provision full VMware clones, where every desktop is created with a fullsized operating system and applications built into the gold image. This increases storage capacity requirements, and makes managing, patching, and updating the virtual desktops no easier than traditional PCs, negating many of the operational efficiencies and cost savings expected from VDI. However, capacity isn’t the real challenge when it comes to dealing with the high cost of VDI storage. Even if you bought enough SAN capacity to thick-provision full desktop clones, you still wouldn’t be able to deliver enough IOPS to give end users a satisfactory virtual desktop experience.
Storage Capacity Requirements for VDI Let’s take a look at a typical VDI use case where an organization needs to support 500 persistent virtual desktops using Microsoft Windows 7. 4
Creating standard full clones would require about 20 GB of storage per desktop to account for Windows itself, standard applications, and space for user data and user installed applications. Multiply 20 GB by 500 desktops, and you would require approximately 10 TB of disk space. Using 450GB SAS drives and a RAID5 configuration, you would need 25 drives to deliver the 10 TB of standard SAN storage required by the 500 virtual desktops.
Storage IOPS Requirements for VDI Now let’s take a look at the same VDI use case from an IOPS perspective. Figure 3 offers an estimated IOPS breakdown for 500 desktops. Using 10 IOPS per virtual desktop requires 5000 IOPS to support 500 desktops, not accounting for storm conditions where IOPS increase significantly; assuming a 30/70 split between read and write IOPS. Supporting 5,000 IOPS with 450GB 15K SAS drives would require 60 drives configured in RAID 5. Caching can reduce the drive numbers, but only slightly given that desktops have heavy write loads, and that full desktop clones will not make the read blocks “hot” enough to store them in the cache.
Read Write Total IOPS
IOPS/VM 3 7
VMs 500 500
Total IOPS 1500 3500 5000
Figure 3 – VDI IOPS Requirement for 500 Virtual Desktops Based on Read/Write Ratios
As you can see, IOPS is the problem, not capacity. Only 25 drives are required to deliver enough usable storage capacity for the 500 desktops, but 60 drives are required to deliver sufficient IOPS. HDD QTY 60
HDD IOPS 180
Raw IOPS 10800
Write %
Subtotal
Penalty
0.7
7560
4.0
Write IOPS 1890
read % 0.3
Read IOPS 3240
Usable IOPS 5130
Figure 4 –VDI IOPS Analysis for 500 Virtual Desktops
Dell EqualLogic Hybrid Arrays Solve the VDI IOPS Problem The Dell EqualLogic PS Series hybrid arrays are designed to support fast access to high demand “hot” data in multi-tiered datasets. The Dell EqualLogic PS6010XVS hybrid array has 16 drives – 8 high performance SSD drives and 8 high capacity 15,000 rpm Serial Attached SCSI (SAS) hard disk drives. The on-board intelligence of the EqualLogic firmware provides automatic tiering between the two drive 5
types – SSD and SAS, as well as automatic load balancing across multiple drives of each type, helping deliver the appropriate balance of responsiveness and capacity for virtual desktop workloads. The arrays use dynamic data placement algorithms to move “hot” data to the SSD drives from SAS drives and move “cold” or “warm” data from the SSD drives out to the SAS drives as needed.
Figure 5 – Automatic Tiering with Dell EqualLogic PS6010XVS The 8 SSD drives and 8 SAS drives in the hybrid arrays provided sufficient IOPS to support the requirements of 500 virtual desktops. However, capacity for persistent desktops is a challenge for the Dell EqualLogic PS6010XVS array, as it delivers 4.4 TB of raw storage capacity. Using RAID6, approximately 2.5 TB of storage capacity remains usable. So although the Dell EqualLogic PS6010XVS provides sufficient IOPS needed by the 500 desktops, the 2.5TB of usable capacity falls short of the 10 TB of usable storage capacity required by the 500 full-sized virtual desktops. This is where using Unidesk in conjunction with Dell EqualLogic hybrid arrays is the ideal combination to solve both the IOPS and capacity challenges that have been holding VDI back.
Unidesk VDI Management Software Solves the VDI Capacity Problem Unidesk VDI management software creates persistent desktops on VMware infrastructure that sustain all user customizations, while delivering the storage savings and single image management benefits of non-persistent desktops. As shown in Figure 6, Unidesk enables desktops to be managed as sets of discrete, reusable “layers.” Every desktop has a personalization layer that sustains all user customizations, from simple profile settings to user-installed applications and plug-ins, enabling IT to implement VDI for more use cases. Figure 6 6 – Unidesk Desktop Layering Offers the Customizable Desktop Experience of Persistent VDI and the Storage Efficiency and Single Image Management of Non-Persistent VDI
However, administrators need only patch and manage a single set of shared application and OS layers for all desktops to dramatically reduce OpEx.
As Figure 7 shows, Unidesk’s ability to share the same OS and application layers across many virtual desktops reduces the disk space capacity required for persistent desktop use cases by upward of 70%. Let’s look at how Unidesk layer sharing impacts our 500 desktop VDI example from a capacity standpoint. By sharing a single copy of Windows 7 and standard applications across many virtual desktops, you would only need to design for approximately 5 GB of storage per desktop as follows: • •
• •
2.5 GB for the boot drive 1 GB for desktop storage (user settings and user-installed applications) 1 GB for shared applications .5 GB for desktop repair snapshots
Figure 7 – Unidesk Shares the Same OS and Application layers across many virtual desktops to reduce VDI disk space requirements up to 70%
Multiplying 5GB by the 500 desktops and 2.5 TB of usable storage capacity is required with Unidesk for the 500 desktops, a 70% reduction compared to the full-sized clones. Since each Dell EqualLogic hybrid array can deliver 2.5 TB of usable capacity, you would only need 1 array to meet the storage capacity requirements of the 500 desktops provisioned and managed by Unidesk. And since only 1 array is required to meet the IOPS requirements as well, you’ve now reduced your VDI storage costs from 4 arrays to 1 array.
More Benefits of Combining Dell Hybrid Arrays with Unidesk Unidesk’s layer sharing also creates a data pattern that makes good use of the intelligent data tiering capabilities of Dell EqualLogic PS Series hybrid arrays. When a Unidesk application or OS layer is assigned to one or more desktops, the desktops directly read that layer without copying or duplicating the data. This enables the array to easily identify those layers as “hot” and retain them on SSD, while pushing the rarely accessed desktop content to SAS. The most-used blocks from the OS layer remain on the low-latency SSD drives, which is especially beneficial for writes given they generally make up 70% of VDI payload. If Unidesk was not used, then 7
the OS blocks would be spread out and too infrequently used to be recognized as “hot,” resulting in increased latency and lower performance, as our testing showed. Using Dell hybrid arrays in tandem with Unidesk also offers data center space management advantages and significant savings in power and cooling as well. Instead of needing many shelves of 15K drives, only 1 hybrid array is needed, with a power footprint of a single shelf.
Test Configuration and Tools To prove that you can increase user density and still deliver plenty of IOPS by provisioning storageefficient desktops with Unidesk on Dell EqualLogic hybrid arrays, Dell DVS built a test environment consisting of Dell servers, a Dell EqualLogic PS Series hybrid array, VMware vSphere virtual infrastructure, VMware View connection brokering software, Unidesk VDI management software, and a variety of applications, as shown in Figure 9.
Figure 8 – Test Lab Configuration for Comparing Capacity and IOPS of Unidesk “Layered” Desktops versus Standard “Full Clone” Desktops
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Testing Method In order to create a valid “apples-to-apples” comparison VMware View 4.6 was tested first to establish the baseline. Unidesk was then integrated into the View environment and tested. All testing was conducted under load using Login Consultant’s Login VSI Pro a benchmarking tool used to measure and report on the performance and scalability of VDI environments. Login VSI Pro uses “Launcher” virtual machines (VMs) that open VMware View sessions to the virtual desktops and execute a set of tests. Upon completion, EqualLogic SANHQ was used to assess storage performance. SANHQ provides centralized monitoring, historical performance trending, and event reporting for EqualLogic PS Series storage. The Login VSI Pro “Medium” work load was used to simulate what is typically referred to as a “Knowledge Worker”. Details of this workload are in the following table.
Login VSI Medium Workload Characteristics Emulates a medium knowledge worker using Office 2010, IE9, PDF and Flash. Once a session has been started the medium workload will repeat every 12 minutes. During each loop the response time is measured every 2 minutes The medium workload opens up to 5 apps simultaneously. The type rate is 160ms for each character Approximately 2 minutes of idle time is included to simulate real-world users. Each loop will open and use: Outlook 2010, browse 10 messages. Internet Explorer 9, one instance is left open (BBC.co.uk), one instance is browsed to Wired.com, Lonelyplanet.com and heavy Flash app gettheglass.com Word 2010, one instance to measure response time, one instance to review and edit document Bullzip PDF Printer & Acrobat Reader, the word document is printed and reviewed to PDF. Excel 2010, a very large randomized sheet is opened. PowerPoint 2010, a presentation is reviewed and edited. 7-zip: using the command line version the output of the session is zipped. Figure 9– Login VSI Medium Workload Characteristics
The Windows 7 master image for the VMware View testing was 21GB. With a capacity use target of 90% of the EqualLogic array, 107 persistent virtual desktops were deployed. While 3 additional desktops could have been deployed across LUNs 2, 3 and 4, it was decided against bringing the LUNs to within 1% of capacity to avoid possible performance implications that might affect results.
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The 107 full VMware View Windows 7 virtual desktops were then tested under load. After the VMware View testing was complete, Unidesk was deployed into the environment and tested under identically configured load in the following test scenarios: 1. 107 Unidesk provisioned virtual desktops to contrast directly with the aforementioned VMware View testing. 2. 361 Unidesk provisioned virtual desktops to produce greater than 3x-to-VMware View comparison
Storage Analysis and Results The results verified that Unidesk desktops performed as well as the thick provisioned, full-sized clones when both were run on the Dell EqualLogic hybrid arrays. As expected, however, the Unidesk provided a much higher virtual desktop density on the same EqualLogic PS Series array without sacrificing performance. Note: Because this testing is based on simulation, and not “real life” desktop use, the number of desktops you will be able to support on a single Dell EqualLogic hybrid array may be more or less in your environment. The Medium simulation may actually be more demanding than normal desktop use, since users are not all active at the same time. The best way to determine the IO requirements in your environment is to perform an assessment of all or a subset of your desktops. The following set of charts represents the VMware View test and is used as the baseline for subsequent analysis of the Unidesk tests. Note that while the capacity of the array is consumed, the IOPS are well below the capabilities of the array at 8000+ IOPS.
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Figure 10 – Storage Results of 107 VMware View virtual desktops under Simulated Desktop Load
Storage Performance Analysis As the next chart shows, the performance of over 3x the number of Unidesk virtual desktops required a little over 3x the IOPS, which is expected. However, while Average Write Latency is excellent in both cases, Unidesk desktops show a significantly lower Average Read Latency especially when considering there are 3x as many virtual desktops running under load, compared to the full VMware View desktops. This is due to the Unidesk CacheCloud architecture sharing common OS and application layers across many virtual desktops. The Dell EqualLogic array sees the blocks from these shared layers as “hot” and stores them on its low-latency SSD drives for improved IO read performance.
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Figure 11 – Storage Results of 361 Unidesk virtual desktops under Simulated Desktop Load
Conclusion: Combining Dell EqualLogic Hybrid Arrays with Unidesk Maximizes IOPS and Minimizes Capacity When Deploying a Dell DVS Enterprise Infrastructure Solution In this paper we have discussed the challenges that result from trying to implement persistent virtual desktops for the large percentage of knowledge workers who require a modern, customizable desktop experience. Provisioning full-sized desktop clones on standard SAN storage requires costly storage capacity that is still insufficient to address desktop IOPS requirements. Using advanced, highperformance hybrid arrays like Dell EqualLogic PS6010XVS that use SAS and SSD in the same chassis deliver enough IOPS, but then capacity can become the bottleneck. Our tests have shown that combining Unidesk VDI Management software with a Dell DVS Enterprise Infrastructure integrated solution stack featuring Dell EqualLogic PS6010XVS hybrid array solves both the capacity and IOPS problems at a greatly reduced cost, while also simplifying VDI image management, application packaging, and persona management. Unidesk layering technology reduces the storage footprint up to 70% compared to full desktop clones, and creates a “hot” data pattern that optimizes the automated tiering of Dell EqualLogic PS6010XVS hybrid array, so that hot blocks are stored on SSD, and less frequently accessed data is migrated to SAS. The result is more IOPS delivered on a smaller storage footprint for greater user density and much lower storage cost/user.
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Product Information Information about Dell EqualLogic hybrid SAN arrays can be found at http://www.equallogic.com Information about Unidesk VDI Management software can be found at http://www.unidesk.com, or by contacting your local Dell sales representative. To learn more about Dell’s Desktop Virtualization Solutions (DVS), please visit http://www.dell.com/virtualdesktops. Dell and Unidesk Corporation have partnered to make Unidesk VDI Management software available for purchase through Dell Software & Peripherals. For more information around the value of DVS and Unidesk, please visit http://www.unidesk.com/dell.
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