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A scientific approach to

XenApp farm sizing

Helge Klein

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Who isHelge Klein?

CTP, MVPAuthor of SetACL and Delprof2Independent consultant and developerArchitect of what later became Citrix Profile Management

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talking about?What is he

Scientifically sound farm sizing methodologyHow to calculate farm capacity

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Methodology

1. Determine capacity of existing farm2. Measure load and identify bottlenecks3. Calculate capacity of new farm

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ExampleDescription Farm capacity

old (total)Farm capacity old (per user)

Factor Farm capacity new (per user)

Farm capacity new (total)

RAM for user sessions [MB] 630,000 315 2.0 630 1,575,000

CPU [normalized cores] 1,250 0.63 0.25 0.16 391

Hard disk [write IOPS] 7,300 3.65 1.5 5.48 13,688

Network [MB/s] 24,000 12.00 0.1 1.20 3,000

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Where to get the

numbers?1. Data collection2. Observation3. Measurements4. Calculation

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Data collection

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for /f %i in (AllFarmServers.txt) do wmic /node:%i cpu get name, maxclockspeed, systemname, description, manufacturer, revision /format:csv >> CPUs.txt

Collect CPU dataCreate AllFarmServers.txt with qfarm

Use resulting list to determine server model

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Srv001,x86 Family 15 Model 4 Stepping 10,GenuineIntel,3400,Intel(R) Xeon(TM) CPU 3.40GHz,1034,Srv001Srv001,x86 Family 15 Model 4 Stepping 10,GenuineIntel,3400,Intel(R) Xeon(TM) CPU 3.40GHz,1034,Srv001Srv001,x86 Family 15 Model 4 Stepping 10,GenuineIntel,3400,Intel(R) Xeon(TM) CPU 3.40GHz,1034,Srv001Srv001,x86 Family 15 Model 4 Stepping 10,GenuineIntel,3400,Intel(R) Xeon(TM) CPU 3.40GHz,1034,Srv001Srv002,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv002Srv002,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv002Srv002,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv002Srv002,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv002Srv002,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv002Srv002,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv002Srv002,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv002Srv002,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv002Srv003,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv003Srv003,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv003Srv003,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv003Srv003,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv003Srv003,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv003Srv003,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv003Srv003,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv003Srv003,x86 Family 6 Model 44 Stepping 2,GenuineIntel,2666,Intel(R) Xeon(R) CPU E5640 @ 2.67GHz,11266,Srv003Srv004,x86 Family 6 Model 26 Stepping 5,GenuineIntel,2666,Intel(R) Pentium(R) III Xeon-Prozessor,6661,Srv004Srv004,x86 Family 6 Model 26 Stepping 5,GenuineIntel,2666,Intel(R) Pentium(R) III Xeon-Prozessor,6661,Srv004Srv004,x86 Family 6 Model 26 Stepping 5,GenuineIntel,2666,Intel(R) Pentium(R) III Xeon-Prozessor,6661,Srv004...

The result

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RAM, NICshard disks

Could be determined via WMI, tooOften knowing the server model is sufficientComponents per model often identical

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Component HP DL360 G4

CPU 2x Xeon dual core 3,0 GHz, no Hyper Threading4 Cores, CPUID: x86 Family 15 Model 4 Stepping 1

RAM 4 GB

NICs 2x Gigabit, 1 connected

RAID Smart Array 6i

Hard disks 2x 70 GB configured as RAID-1, Compaq BF0728A4CB, 3,5“, 15.000 R/Min, Ultra320 SCSI

Spec sheet

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Resulting dataServer model NumberDL360 G7 26DL360 G6 52DL360 G5 70DL360 G4p 60DL360 G4 35

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Observation

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How many users are logged on?Load of CPU, RAM, NICs

Individual processes with a lot of RAM or CPU?

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Physical Disk\% Disk Time

Physical Disk\Avg. Disk Queue Length

„Time“ is equivalent to flickering of hard disk LEDDisk queue length: Number of waiting IOs

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Hypothesis: farm is

memory limited

Limiting factor will differ between farms

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Measurements

Tool: PerfmonNext slides: relevant counters

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Terminal Services\Active SessionsTerminal Services\Inactive Sessions

Terminal Services\Total SessionsSystem\Processes

General system information

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PhysicalDisk(_Total)\% Disk TimePhysicalDisk(_Total)\Avg. Disk Queue Length

PhysicalDisk(_Total)\Disk Reads/secPhysicalDisk(_Total)\Disk Writes/sec

PhysicalDisk(_Total)\Avg. Disk sec/Transfer

Hard disk activityLoad, queue length, operations per second, latency

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Processor(_Total)\% Processor TimeMemory\Available MBytes

Network Interface(*)\Bytes Total/sec

CPU, RAM and networkRAM: total amount must be known!

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logman create counter TSPerf -f csv -cf C:\PerfLogs\Counters.txt -o C:\PerfLogs\Server13.csv -si 60 -rf 24:00:00

AutomationCreate and start data collector set. Format CSV, performance counters are

read from C:\PerfLogs\Counters.txt, output file is C:\PerfLogs\Server013.csv, 60 second sampling interval, duration 24 hours.

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logman create counter TSPerf -f csv -cf C:\PerfLogs\Counters.txt –o C:\PerfLogs\Server13.csv -si 60 -rf 24:00:00-s Server13

Execution on remote computer Server13

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for /f %i in (Servers.txt) do logman create counter TSPerf -f csv -cf C:\PerfLogs\Counters.txt -o C:\PerfLogs\%i.csv -si 60 -rf 24:00:00 -s %i

Many serversOne computer name per line in Servers.txt

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Analyzingthe measured data

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CPU and sessions

Server 37

Moderate load during logon phase,

afterwards even less

A lot of overcapacity

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CPU and sessions

Server 89

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Overlaying the CPU load of

many servers

Easily verify the analyis

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HDD and sessions

Server 37

Moderate load, peaks during logon phase

Full load at aprox. 200

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HDD and sessions

Server 89

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Overlaying the HDD load of

many servers

Easily verify the analyis

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RAM and sessions

Server 37

Continually increasing load, maximum in the

afternoon

Available RAM must not go near zero

(because of disk cache)

High load

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RAM and sessions

Server 89

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Overlaying the memory load

of many servers

Easily verify the analyis

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Network and sessions

Server 37

200 = 2 MB/s

Average rate < 200 KB/s

Very low load, a lot of overcapacity

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Network and sessions

Server 89

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Overlaying the network load

of many servers

Easily verify the analyis

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Hypothesis confirmed: farm is limited by

available memoryCPU load: low, network: negligiblehard disk: moderate

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Calculatingfarm capacity

Description Farm capacity old (total)

Farm capacity old (per user)

Factor Farm capacity new (per user)

Farm capacity new (total)

RAM for user sessions [MB] 630,000 315 2.0 630 1,575,000

CPU [normalized cores] 1,250 0.63 0.25 0.16 391

Hard disk [write IOPS] 7,300 3.65 1.5 5.48 13,688

Network [MB/s] 24,000 12.00 0.1 1.20 3,000

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How to compare performance of different CPUs?Benchmarking is difficultBetter: Moore’s law (doubling of performance every 18-24 months)Surprisingly accurate (amongst other things because it is a self-fulfilling prophecy)

NormalizingCPU performance

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Performance after time (in months)Assumed performance doubling every 21 monthsOldest CPU in farm = 1,0

𝐿(𝑡 )=𝑒0,033𝑡

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CPU Cores First sold Performance index Performance index per core

Xeon 7100 „Tulsa“ 3,0 GHz

2 08/2006 1,0 1,0

Xeon 7100 „Tulsa“ 3,4 / 3,6 GHz

2 03/2007 1,26 1,26

Xeon E5430 / E5440

4 11/2007 1,64 0,82

Xeon X5550 4 03/2009 2,78 1,39

Xeon E5640 4 03/2010 4,13 2,06

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CPU Number of CPUs

Number of cores

Number of normalized CPUs

Number of normalized cores

Xeon 3 GHz 70 140 70 140

Xeon 3,4/3,6 GHz

119 238 150 300

Xeon E5430/E5440

70 280 115 230

Xeon X5550 67 268 186 370

Xeon E5640 26 104 107 210

Total 352 1030 628 1250

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Farm capacity:

1250 normalized CPUs

0.63 CPUs / user

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Hard disk performance =

IOPSWith many concurrent accesses transfer rate is mostly irrelevantMore important: IOPS (operations per second)Exact number depends on measurement method do not believe vendors

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PhysicalDisk(_Total)\Disk Reads/secPhysicalDisk(_Total)\Disk Writes/sec

IOPS measurement with PerfmonRead and write IOPS may be very different

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Read and write IOPS

Average: ~15

Including spikes: 30

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Farm capacity:

7300 IOPS

3,7 IOPS / user

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RAM – how muchdo we have?

We need total RAM that is available for user sessions

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Server model RAM / server [GB] #Servers RAM / server total [GB]

DL360 G4 3,5 35 122,5

DL360 G4p 3,5 60 210

DL360 G5 3,25 70 227,5

DL360 G6 3,49 52 181,48

DL360 G7 3,49 26 90,74

Total 243 832

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Description Memory [MB]

Session 0 (OS + Presentation Server + antivirus) 325

Kernel (pooled + non-pooled) 175

File system cache 400

Total 900

Calculate RAM used by the OS (Server 2003)

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Farm capacity:

630 GB

315 MB / user

25% Overhead because 900 MB used by OS

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Network – too much for HDX?

1 Gigabit/second per server~ 100 MB/s

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Farm capacity:

24 GB/s

12 MB/s / user

Extreme overcapacity

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Futurecapacity

Description Farm capacity old (total)

Farm capacity old (per user)

Factor Farm capacity new (per user)

Farm capacity new (total)

RAM for user sessions [MB] 630,000 315 2.0 630 1,575,000

CPU [normalized cores] 1,250 0.63 0.25 0.16 391

Hard disk [write IOPS] 7,300 3.65 1.5 5.48 13,688

Network [MB/s] 24,000 12.00 0.1 1.20 3,000

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Parameters. Calculation includes:Changed user count, different memory requirements of new OS,server replacement, capacity increase for disaster recovery

Parameter Value

Farm users old (CCU) 2,000

Farm users new (CCU) 2,500

RAM for OS new [MB] 1,300

CPU performance new [normalized cores]

1.9

IOPS per disk new 300

Reserve for disaster recovery 1.5

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Servers are memory limited after setting the amount of RAM,the other parameters can be calculated

Virtual server

RAM [MB] 32.768

User sessions 49.9

CPU cores (physical) 4.1

IOPS 273

NICs 0.6

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After setting the number of VMs per host the other parameterscan be calculated.Excel sheet available upon request.

Physical serversVMs per host 3 #Virtual

servers50

RAM [MB] 101,376 #Hosts 25

CPU cores 12 Users / host

150

Hard disks 3

NICs 2

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Thank you!Helge Klein