VDI Design Guide
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This document provides guidance on designing a virtual desktop infrastructure (VDI). It discusses key decision points around the hypervisor, servers, and storage. It recommends determining user groups, applications, and requirements through piloting before finalizing the design. The document also analyzes options for the hypervisor, servers including CPU, memory, and local storage considerations, and storage including the impact of VM density and hidden capacity needs. Monitoring IOPS and latency is emphasized as critical to ensuring a successful VDI deployment.
VDI Design Guide
- 1. VDI DESIGN GUIDE Hypervisor | Server | Storage
- 2. What Would Dan Do? Blog: http://www.danbrinkmann.com Twitter: @dbrinkmann VMware vExpert 2012
- 3. Decision Points • Hypervisor • Server • Storage
- 5. Before You Go Further • Have a business reason • Determine user groups and applications • Determine requirements • Pilot • Gather data
- 6. Design • VM’s per host • Hosts per cluster • Management infrastructure limits • Storage IO / capacity limits
- 7. Hypervisor Choices Options • VMware vSphere 85% - 90% • Citrix XenServer 10% - 15% My experience • Microsoft Hyper-V ~0% • VMware View = vSphere hypervisor
- 8. Hypervisor Choices XenServer • Storage stack • NFS is the best option • LVM over iSCSI or FC is confusing for “Windows” people • Storagelink…/sigh • Lack of 3rd party integration • Lack of skilled engineers in the market • Management built in to hypervisor (XenCenter)
- 9. Hypervisor Choices Microsoft Hyper-V • 2008 R2 not relevant • Hyper-V 2012 • Offloaded data transfer • No more redirected mode • Additional storage options • CSV cache http://blogs.msdn.com/b/clustering/archive/2012/03/22/10286676.aspx • 3rd party integrations • Network teaming support
- 10. Hypervisor Choices Which one should I choose? • vSphere • Most features • Broadest support among vendors • Largest base of skilled engineers • Most number of 3rd party integrations • Highest cost • Translate: least amount of brain damage (today)
- 11. Should I Virtualize vCenter? • Consider an infrastructure cluster Management VM’s Virtual Desktops VMware vSphere VMware vSphere Servers Servers
- 12. Should I virtualize vCenter? • Use VM-Host affinity rules
- 13. Servers Determine a Lot • Storage options • Density – cpu/memory • High availability design
- 14. First Some Virtual Desktop Fallacies • vCPU count • vCPU to pCore overcommit • Memory requirements • Storage IO requirements • Don’t believe vendor estimates
- 15. Servers - Rackmount vs Blades • Supermodel or the girl next door
- 16. Servers - Rackmount vs Blades Failure domain • Blade chassis vs individual rackmount server • Design for N+1 blade chassis • Blade chassis failures I’ve seen • Backplane failure • Integrated networking (interconnect) failure
- 17. Servers - Rackmount vs Blades Local disk • Blade chassis local disk limited and/or expensive • PCI-Express cards not always available as mezzanine option • Desktop persistence
- 18. Servers – CPU Hypervisor (vSphere) CPU scheduler “When making scheduling decisions, the ratio of the consumed CPU resources to the entitlement is used as the priority of the world. If there is a world that has consumed less than its entitlement, the world is considered high priority and will likely be chosen to run next.” http://www.vmware.com/resources/techresources/10131
- 19. Servers - CPU Compute with a physical PC OS/Apps/Profile CPU 1
- 20. Servers - CPU Compute in RDSH / XenApp OS/Apps/Prof OS/Apps/Prof OS/Apps/Prof OS/Apps/Prof OS/Apps/Pr ile OS/Apps/Pr ile OS/Apps/Pr ile OS/Apps/Pr ile ofile ofile ofile ofile CPU 1 CPU 2
- 21. Servers - CPU Compute in VDI CPU 1 CPU 2
- 22. Servers - CPU CPU utilization – not enough
- 23. Servers - CPU This is proper CPU monitoring Display Metric Threshold Explanation Overprovisioning of vCPUs, excessive usage of vSMP or a limit(check CPU %RDY 10 %MLMTD) has been set. Excessive usage of vSMP. Decrease amount of vCPUs for this CPU %CSTP 3 particular VM. This should lead to increased scheduling opportunities. The percentage of time spent by system services on behalf of the CPU %SYS 20 world. Most likely caused by high IO VM. Check other metrics and VM for possible root cause The percentage of time the vCPU was ready to run but deliberately wasn’t scheduled because that would violate the “CPU limit” CPU %MLMTD 0 settings. If larger than 0 the world is being throttled due to the limit on CPU. VM waiting on swapped pages to be read from disk. Possible cause: CPU %SWPWT 5 Memory overcommitment.
- 24. Servers – 2 Socket vs 4 Socket Failure domain • Smaller host = less desktops affected • Smaller host might also mean more clusters
- 25. Servers – 2 Socket vs 4 Socket Local disk options (rackmount) • 2 socket servers 8-26 bays • 4 socket servers 8-16 bays 16 drives * 175 IOPs = 2800 IOPs (not RAID adj)
- 26. Servers – 2 Socket vs 4 Socket $$$ Price $$$ • Historically 4 socket servers have not been a linear price increase from 2 socket servers …so is that still true today?
- 27. Servers – 2 Socket vs 4 Socket Sample pricing • 2 socket Intel E5-26xx 8c, 384GB RAM ~$15,500 • 4 socket Intel E5-46xx 8c, 768GB RAM ~$32,000- $36,500 ~3% - 18% premium
- 28. Servers - CPU • More cores is more better (E5 8c, E7 10c) • AMD vs Intel
- 29. Servers - Memory • Buy a lot of it! • Do not run out! • 16GB DIMM size is common • 24 DIMM slots means 384GB
- 30. Servers – Hidden Memory Requirements • Memory overhead • Number of vCPU • Amount of RAM • Amount of vRAM • 3D support • Memory pressure • http://kb.vmware.com/selfservice/microsites/search.do?language=en _US&cmd=displayKC&externalId=1033687 • minFreePct 2%-6% • 6% of 384GB is 23GB • Hypervisor requirements • Storage caching (CBRC, CSV cache)
- 31. Storage VM’s per datastore / LUN • VAAI (ATS) • 4.1 – 2, 5.0 U1 all 8 http://blogs.vmware.com/vsphere/2012/05/vmfs- locking-uncovered.html • <140 per datastore
- 32. Storage Local disk • Will most likely impact server hardware decision • Small failure domain • Spinning disk limitations • SSD or PCI-E NAND-flash options • Non-persistent virtual machines
- 33. Storage iSCSI vs Fibre Channel vs NFS • iSCSI vs Fibre Channel • NFS • Best option XenServer • Cluster size options in vSphere 5 U1 • Don’t make choice for “performance” reasons
- 34. Storage Hidden capacity requirements • vswp file (equal to memory size minus reservation) • vswp file for memory overhead • pagefile • Identity disk (XenDesktop) • Differencing disk
- 35. Storage – Monitoring • IOPs - #1 reason for VDI failure • Latency
- 36. Summary • Do not choose hardware first