MAXIMIZING DESKTOP VIRTUALIZATION SUCCESS WITH VDI-OPTIMIZED DELL EQUALLOGIC HYBRID ARRAYS

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1 SOLUTION PROFILE MAXIMIZING DESKTOP VIRTUALIZATION SUCCESS WITH VDI-OPTIMIZED DELL EQUALLOGIC HYBRID ARRAYS MARCH 2011 In recent years, we have witnessed great technology leaps from all of the leading virtual desktop infrastructure (VDI) software vendors, broadening the scope of potential use cases for server-hosted desktop virtualization. VMware, in particular, upped the performance ante with View 4.5 s storage optimizations. These enhancements eliminate many of the limitations that have constrained VDI storage efficiency to date, and they open up new avenues for solution providers to lower VDI storage capacity requirements and to turbo-charge VDI workload performance. VDI has often promised more than it delivered, due to stubborn complexity, performance and cost challenges. Chief among these challenges has been the high up-front capital costs and subsequent inefficiencies of the storage platforms deployed to support it storage costs are at the heart of the VDI ROI equation. We covered these challenges in detail in the first part of this three-part series. Building on deep integration with VMware s vsphere 4.1 platform via the vstorage APIs, Dell has set its sights squarely on VDI and aims to break down both the cost of acquisition and TCO (CapEx and OpEx) barriers that have plagued VDI ROI in the past. Moving quickly to capitalize on VMware s innovation, Dell has added intelligent workload tiering and new hybrid SSD/SAS arrays to its Equal- Logic PS Series family (the PS6000XVS and PS6010XVS). In this second part of our series, we take a close look at a recent performance benchmark to evaluate in detail how Dell s innovations reduce complexity, improve performance and lower the cost of VDI. VDI DEMANDS HIGH-DENSITY VIRTUALIZATION At first glance, it seems obvious that the consolidation, efficiency and mobility benefits of server virtualization should translate easily to VDI. As widely understood by many practitioners, however, desktop virtualization has a number of unique aspects that make those benefits harder to realize (covered at length in the Taneja Group report Breaking Down the Barriers to VDI). Essentially, it all comes down to density. In order to justify VDI, desktop VMs must be deployed at much higher densities than server VMs at least five to ten times higher in many cases. But dense VM deployments tend to expose performance problems and edge conditions throughout the virtual IT stack, from memory and CPU contentions to I/O bottlenecks. Of course, high densities in VDI are only possible because desktop workloads are intermittent and variable. Unfortunately, this also makes them difficult to model and prone to wild load spikes, which can negatively affect the end-user s desktop experience. Copyright The TANEJA Group, Inc All Rights Reserved. 1 of 10

2 THE IMPACT OF DENSITY ON STORAGE Desktop workloads were designed for local, dedicated disks that are generally much faster than users need them to be. With VDI, tens or hundreds of workloads access shared disks simultaneously and demand fluctuates throughout the work day. This makes it very difficult to guarantee user experience levels without over-provisioning storage capacity and throughput for the worst case. The hypervisor layer complicates matters further. I/O from multiple workloads is consolidated and concentrated, which transforms potentially sequential I/O requests into random ones. Randomized I/O severely degrades the efficiency of traditional storage caching algorithms, leaving VDI performance highly sensitive to disk latency. Variable and consolidated desktop workloads also give rise to intermittent load spikes. These I/O storms can occur when many users simultaneously log in, open the same application, run a virus scan, or perform some other common disk-intensive operation. I/O storms, when combined with the generally sporadic nature of desktop data access patterns, have stalled many VDI projects in their early proof-of-concept stage. In addition to requiring high levels of sustained aggregate I/O throughput, measured in IOPS (I/O operations/second), consolidated desktop workloads often exhibit wide variability in storage I/O read/write ratios. These can vary from as high as 90/10 or greater during boot storms and periods when many users launch the same applications, to 30/70 during the day when most users are viewing and modifying files. Read/write ratios are important, since writes are generally more expensive than reads, and they depend on a complex matrix of factors, including hypervisor memory management effectiveness, array write-back cache performance, and the particular mix of desktop applications in use. In the end, delivering consistent, predictable, and cost effective performance for high-density VDI requires innovation in both the hypervisor and storage layers, and deep integration between the two. Only a centralized storage infrastructure designed to handle these challenges without massive over-provisioning can hope to compete on cost against the current PC desktop status quo. VMWARE VIEW 4.5: OPTIMIZING STORAGE IN THE HYPERVISOR LAYER VMware View includes a complete suite of tools for delivering desktops as a managed service. Recognizing that higher VDI densities are required in order to improve the cost modeling picture for new View deployments, VMware has introduced support for tiered storage in View Composer as part of its recent View 4.5 release. Tiered storage adds storage performance optimization to View s storage capacity optimization features, which include Linked Clones and vstorage Thin Provisioning. Linked Clones and Thin Provisioning View Composer Linked Clones are desktop images that share virtual disks with a common base image, called a Replica. Linked clones can be configured manually or automatically, and set up to be persistent (state is retained and the image is assigned to a user) or non-persistent (refreshed to match the Replica at each login and assigned temporarily to users for certain activities). View 4.5 Composer starts with a Replica (or parent) and can create many Linked Clones from each replica, each acting like an independent desktop with a unique name and host IP address but requiring only a fraction of the disk space needed for a full desktop. Linked clones can reduce storage capacity requirements by 50% to 90% by avoiding storage duplication, since only the deltas from Copyright The TANEJA Group, Inc All Rights Reserved. 2 of 10

3 the parent image are captured in each clone. With vstorage thin provisioning, disk is only allocated to replicas and linked clones as it is written, reducing storage capacity requirements even further. View 4.5 Storage Tiering With storage tiering, the virtual desktop can be further decomposed by placing replicas and linked clones on different datastores with different performance characteristics. For example, replicas can be placed on SSDs, which have lower storage capacity but extremely high read performance, typically supporting tens of thousands of IOPS. Linked clones can then be placed on traditional spinning disks, which provide lower performance but are less expensive and deliver higher capacity, making them well-suited for storing the many linked clones in a large pool. This VMware enhancement enables higher VDI densities, linear scalability, and lower latency, but only when combined with a storage platform designed to leverage hypervisor-layer storage tiering. Indeed, VMware s implementation guidelines state that View 4.5 storage tiering is designed only for specific storage configurations from vendors who offer high-performance disk solutions. Customers are advised not to store replicas on a separate datastore if their storage hardware cannot deliver very high read performance. EQUALLOGIC PS SERIES XVS ARRAYS: HYBRID DESIGN PLUS AUTO-TIERING In Dell s EqualLogic PS6000XVS (and PS6010XVS with 10GbE connectivity) SAN arrays, eight highperformance 100GB SSD drives and eight high-capacity 450GB 15K rpm SAS drives are combined with intelligent, automatic workload tiering in a storage platform designed to support just the types of variable, multi-tiered workloads common in high-density VDI environments. The hybrid PS6000XVS offers the low latency of SSD with the high capacity of SAS in one single EqualLogic array member. These two storage tiers provide the foundation for optimizing the performance of multi-tiered workloads within an array. To leverage this capability, Dell has expanded on the PS Series family s built-in volume and network load balancing with new and innovative Automatic Tiering software that brings intelligence to the autonomic movement of workloads at the sub-volume level. EqualLogic s intelligent software automatically places the linked clone parent replica image on the low-latency, high-performance SSD tier to ensure maximum throughput, while temporary data as well as users unique application data is placed on lower cost, capacity-optimized SAS drives. FIGURE 1. PS6000XVS and PS6010XVS Automated Sub-Volume Workload Tiering Source: Dell Copyright The TANEJA Group, Inc All Rights Reserved. 3 of 10

4 To do this, the PS6000XVS categorizes workloads as hot (high I/O), warm (medium I/O), or cold (low I/O), and then places them, as appropriate and automatically, onto either SSD or SAS disk tiers with no operator intervention required. Figure 1 illustrates this behavior in action. Three volumes are being added to the array one for the gold (linked clone parent replica) image volume and two other volumes for linked clones. I/O storms and other activities will make the gold image volume hot. Additionally, some blocks in linked clone volumes might also become hot due to heavy I/O activity. PS6000XVS automatically moves all the hot data to the SSD tier over time. The PS6000XVS and PS6010XVS can thus perform workload optimization even on volumes containing a mix of workload types and storage needs. In a VMware View 4.5 environment, the benefits are immediately apparent: LOWER VDI COSTS by executing workloads on the most cost-effective storage media; HIGHER PERFORMANCE by placing read-sensitive replica images on low-latency SSD media; SIMPLER OPERATIONS via automated and intelligent on-board tiering software. And, when they are combined with the PS Series ease of installation and operational simplicity, these benefits are sure to make a significant dent in the overall TCO for any VDI implementation. TESTING VDI PERFORMANCE OF THE PS6000XVS WITH VIEW 4.5 To validate these benefits, Taneja Group recently worked with Dell to review and analyze the results of internal performance benchmark testing. Our primary objective was to determine the upper limits of VDI density that can be achieved currently using VMware View 4.5 when deployed against a single PS6000XVS array, leveraging the latest storage capacity and performance optimization features provided by both platforms. As we analyzed Dell s results, we kept the top VDI storage problems in mind: COMPLEXITY: how difficult is XVS set up, configuration, and on-going management? How is data protection handled? How well are desktop image management tools integrated with XVS storage management processes? PERFORMANCE: how much aggregate throughput (IOPS) can be achieved within acceptable storage latencies? How does storage latency contribute to end-to-end virtual desktop latency and compare to network and hypervisor memory latencies? How does the XVS respond to varying workload demands and spikes over time? COST EFFICIENCY: how does the XVS architecture scale up (in capacity and performance) and scale out (balance load across SAN components)? How does it optimize storage utilization or reduce capacity requirements to improve value for each storage dollar spent? VDI DENSITY TESTING ENVIRONMENT View 4.5 Functional Components Solution components included VMware View 4.5 s Connection Manager, vcenter Server and View Composer, and the vsphere 4.1 platform (ESX Server), as illustrated in the functional diagram below (Figure 2). Virtual desktop VMs were deployed to ESX Server hosts using shared iscsi storage. Copyright The TANEJA Group, Inc All Rights Reserved. 4 of 10

5 Virtual Desktop Workload Simulation Dell used the VMware Desktop Reference Architecture Workload Code (RAWC) to simulate virtual desktop workload. RAWC is a freely available and widely used tool developed by VMware that generates a realistic, adjustable desktop workload by running various typical office applications in each of any number of desktop virtual machines. Test Environment Configuration The test server environment consisted of a single Dell PowerEdge M1000e Blade Enclosure configured with a set of sixteen Dell PowerEdge M610 blade servers allocated to various test functional roles. Dell Power- Connect switches were used for LAN and SAN fabrics, and a single PS6000XVS array was configured, as illustrated in Figure 3. For additional details, see Dell s VDI storage sizing and best practices white paper. FIGURE 2. Components of a View 4.5 Infrastructure FIGURE 3. Test Environment Logical Diagram View Client Servers 13x Dell PowerEdge M610 1x 8-host Cluster 1x 5-host Cluster Dell PowerEdge M1000e Blade Enclosure Infrastructure Servers 3x Dell PowerEdge M610 vcenter Server View Connection Manager Domain Controllers Exchange/MSSQL Servers RAWC Session Launchers IP Network 3x Dell PowerConnect M6220, M6348, 6248 Ethernet Fabric Storage Array 1x Dell EqualLogic PS6000XVS 8x 450GB 15K rpm SAS 8x 100GB SSD Copyright The TANEJA Group, Inc All Rights Reserved. 5 of 10

6 View 4.5 Desktop Pool Configuration Linked clone desktop pools were used for testing. Each linked clone functions as an independent desktop VM with a unique identity and can be set up as persistent or non-persistent. All linked clones, as we ve described, share a base replica OS image. As clones are used, temporary system data and user data generated by and unique to each clone are written to storage separately, and can be deleted at the end of the user session (non-persistent). For persistent clones, data such as the user profile and user-generated application data can optionally be redirected to a persistent storage location. Non-persistent desktops require that the Windows user profile be rebuilt on every login, which we expected (and verified) would generate higher I/O and processing loads. For this reason, we chose non-persistent desktops for our reported density results below, as this is a higher-stress use case. Each master replica image was configured with 15GB disk space, one virtual CPU, and 1GB RAM. Replicas and clones were allocated to different volumes. Each automated pool had an always on power policy, PCoIP display protocol, and an aggressive setting for storage overcommit. PS6000XVS Configuration For the non-persistent desktop tests, the eight-host desktop VM server cluster was allocated four volumes on the PS6000XVS array, each mounted as a VMware VMFS datastore. One 32GB volume contained the master replica image, and three 500GB volumes were allocated for clones. The fivehost cluster was given a 32GB volume for the replica and two 500GB volumes for clones. The PS6000XVS array provides approximately 2.5TB of usable storage capacity (accelerated RAID- 6). VMware View 4.5 best practices for capacity planning recommend that for a clone pool of the size chosen (1,014 clones provisioned with 2GB storage each for delta disk growth) approximately 2,333GB should be allocated. This conservative capacity plan allowed for reasonable disk usage growth across the linked clones in each pool; slightly higher density could have been achieved by relaxing this utilization limit. RAWC Workload Profile Configuration From a storage viewpoint, VDI density is primarily limited by array capacity and the maximum sustained IOPS the array can deliver within acceptable I/O latency limits. For the results below, an upper bound of 20ms on I/O latency was used, which is a generally accepted limit. RAWC was then used to define and tune a single simulated virtual desktop workload profile, with a target steady-state requirement of 3-5 IOPS. This workload profile simulates usage patterns for a typical task worker and includes a limited set of repetitive tasks within a small set of applications, such as the type of work done in a call center or by administrative staff. VDI DENSITY TEST RESULTS Login Storm Performance Results Figure 4 shows the storage group I/O as measured by SANHQ at the peak of the login storm phase (top chart). The 50/50 read/write ratio was as expected: each login event requires a high number of reads from the replica master as well as a high number of writes as the non-persistent desktop clone recreates a user profile and performs other tasks associated with a first-time login. The array delivered an impressive 8,607 total average IOPS during the login storm with latency less than half of our established upper limit. Copyright The TANEJA Group, Inc All Rights Reserved. 6 of 10

7 FIGURE 4. Login Storm Group I/O and Disk IOPS Source: Dell Figure 4 (bottom chart) shows I/O performance measured per disk at the same login storm peak. The detailed data in the table indicates that during peak load approximately 90% of the array IOPS were served by the SSD drives. This was as anticipated: during the login storm, heavy read I/O is targeted at the master replica image, which should cause this data to become hot and trigger an automatic movement of the replica to the SSD tier. As SSD drives deliver significantly higher random read I/O performance than 15K SAS drives, the automated tiering dramatically improved the array s overall I/O performance during the login storm. Network utilization remained well within the 480 MB/s available, with a maximum of 31.3% utilization. In addition, all four PS6000XVS ports were properly load-balanced, with each handling approximately 25% of the storage network traffic. Copyright The TANEJA Group, Inc All Rights Reserved. 7 of 10

8 Steady-State Performance Following the login storm, once all of the desktop sessions had launched and were in operation, we continued to observe performance. During steady-state read/write ratios changed. We expected to see much higher write percentages and this was confirmed: in steady-state, the average total IOPS generated was 3,200 (approximately 3.2 IOPS per task worker desktop), of which 25% were reads and 75% writes, while latency remained below 5ms on average (Figure 5, top). The lower chart in Figure 5 shows I/O performance at the disk level at the same point during the steady-state phase. The detail table indicates that approximately 85% of the array IOPS were served by the SSD drives, with 15% served by the 15K SAS drives. The increased I/O load on the SAS drives here was expected: steady-state application use should generate a high write percentage (75% in our tests) and a significant portion of this I/O is directed at the differential (delta) disks of the individual desktop virtual machine clones. FIGURE 5. Steady-State Group I/O and Disk IOPS Source: Dell Copyright The TANEJA Group, Inc All Rights Reserved. 8 of 10

9 ANALYSIS AND OBSERVATIONS: WHAT IT MEANS Enterprises considering a large-scale VDI deployment should take note of several important observations from the test results we ve presented: Automated Workload Tiering Delivers Performance The test results clearly show that Dell s intelligent Automatic Tiering placed the hot master replica image during the start-of-day login storm on the high-performance SSD, as anticipated. When the login storm subsided, the PS6000XVS gracefully transitioned to the new workload demands and read/write ratios of the steady-state task worker scenario. Even at the high density of 1,014 task worker desktop images, the PS6000XVS was able to meet the peak workload (a noteworthy 8,600 IOPS during the login storm) with performance headroom to spare. Also, the PS6000XVS was able to store all 1,014 desktop VM images while maintaining 15% spare capacity (each VM image was provisioned with at least 2GB for its linked clone delta disk). We also noted that Dell s efficient use of SSD for write staging was highly effective, ensuring balanced performance even as read/write ratios shifted drastically. Utilizing a portion of the SSD tier as extra write cache is a valuable PS Series innovation, and once again is fully automated the array determines how much flash to allocate and the administrator never needs to worry about configuring cache read/write allocations. THE PS6000XVS DEPLOYED IN CONJUNCTION WITH VMWARE VIEW 4.5 REPRESENTS A SIGNIFICANT LEAP FORWARD IN VDI DENSITY. THESE RESULTS INDICATE THAT THE PS6000XVS STRIKES THE OPTIMAL BALANCE BETWEEN STORAGE PERFORMANCE AND CAPACITY MAKING IT EXCEPTIONALLY WELL- SUITED TO VDI ENVIRONMENTS. Load Balancing Everywhere Delivers Automation and Simplicity In our view, the PS Series arrays definitely raise the bar for large-scale VDI deployments. When combined with the flexibility of View 4.5 s storage tiering options, the across-the-board load balancing provided by the PS Series becomes even more powerful and pronounced. The PS6000XVS exhibited true load balancing everywhere: not only across spindles, but across network ports, controllers, volumes, disk types and even within each disk type. Provisioning was a simple matter of a few clicks; RAID settings were easy to configure using default parameters in the PS Series intuitive Group Manager software. Administrators do not have to worry about detailed space allocations the array distributes workloads within broadly-defined volume settings automatically. Performance monitoring was also simplified Dell s no-cost included SAN HeadQuarters provided rich top-level views as well as point-and-click drill down into detailed volume, group, disk, and network metrics. The investments Dell has made in management tools, in our view, will significantly lower the on-going operations costs for VDI deployments of all sizes. This PS Series benefit should be a key element in customer acquisition and TCO cost modeling when planning a new or expanded VDI project. Copyright The TANEJA Group, Inc All Rights Reserved. 9 of 10

10 Solution Profile PS Series Architecture Delivers Cost-Efficient Scale Up and Scale Out Support for more than 1,000 task worker desktops on a mid-range array is headline-worthy in and of itself. This means that the cost-of-acquisition hurdle stalling many VDI deployments can be overcome, with a per-virtual-desktop array cost heading below the cost of a hard drive in a typical physical desktop. This makes VDI much more compelling. And it means VMware View customers can start small and still receive excellent value for each VDI storage dollar spent. But for the PS Series, this is just a starting point. Because the PS Series is based on a peer storage architecture, every component scales linearly with the addition of new arrays capacity, controller throughput, network bandwidth, etc. This means that scale up and scale out are both cost-efficient: the same economies of scale gained by the PS Series architecture for VDI will extend to multiple thousands of virtual desktops and we fully expect Dell to continue to improve efficiency through further enhancements to its industry-leading automated tiering software. This is true pay as you grow cost efficiency. TANEJA GROUP OPINION Dell s EqualLogic PS6000XVS and PS6010XVS arrays are designed to support fast access to high demand hot data in a multi-tiered workload environment. The use of two drive types SSD and SAS in a single array, plus automatic tiering of workloads across drive types, makes the PS6000XVS/PS6010XVS a very cost-efficient solution for VDI. The VDI density test results Taneja Group has validated so far bode very well for a great leap in VDI storage density from Dell. Our analysis of the test results showed that the Dell PS6000XVS, for a typical set of linked-clone non-persistent VDI task workers, easily achieved a density of more than 1,000 virtual desktops with headroom. We are impressed by Dell s investment in VDI overall and in particular with the pace at which Dell develops array innovations to quickly capitalize on new VMware storage optimization technologies. This tight working relationship ensures that Dell EqualLogic customers will remain at the leading edge of efficiency in their VMware VDI deployments moving forward. As we saw in the testing, the PS Series leverages View 4.5 enhancements transparently and without additional operations overhead. What does this mean? Dell has delivered a powerhouse storage platform that effectively eliminates the performance problems caused by read-sensitive shared master replicas in high-density VDI environments. This is headline-worthy performance. Maybe it s time to review your VDI ROI calculations? THE INFORMATION CONTAINED HEREIN HAS BEEN OBTAINED FROM SOURCES BELIEVED TO BE ACCURATE AND RELIABLE, AND INCLUDES PERSONAL OPINIONS THAT ARE SUBJECT TO CHANGE WITHOUT NOTICE. TANEJA GROUP DISCLAIMS ALL WARRANTIES AS TO THE ACCURACY OF SUCH INFORMATION AND ASSUMES NO RESPONSIBILITY OR LIABILITY FOR ERRORS OR FOR YOUR USE OF, OR RELIANCE UPON, SUCH INFORMATION. BRANDS AND PRODUCT NAMES REFERENCED HEREIN MAY BE TRADEMARKS OF THEIR RESPECTIVE OWNERS. Copyright The TANEJA Group, Inc All Rights Reserved. 87 Elm Street, Suite 900 Hopkinton, MA T: F: of 10