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.

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