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Load Balancing and Intelligent Load Balancing. Jesús González Escalation Engineer. Deep understanding of load balancing architecture Troubleshooting techniques Identify the root cause of any LB problem. Objectives. Architecture Data Collector Updates - Examples Performance Data Helper

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load balancing and intelligent load balancing

Load Balancing and Intelligent Load Balancing

Jesús González

Escalation Engineer

objectives
Deep understanding of load balancing architecture

Troubleshooting techniques

Identify the root cause of any LB problem

Objectives
agenda
Architecture

Data Collector

Updates - Examples

Performance Data Helper

Citrix and the PDH

Where can it go wrong?

Black hole effect (Load Throttling - Intelligent Load Balancing)

Some servers get all the connections

Full load after installing an MUI

Troubleshooting

Agenda
architecture5
Architecture

Data Collector DC - Dynamic Store DS

LmsSS.dll - IMA Subsystem

LMS20Rules.dll - System counters

MFRules.dll - XA counters

PDH.dll - Performance Data Helper

data collector updates
Data Collector is updated every 30 s

Only when the change in the load evaluator is bigger than 5%

Every 5 minutes we send a full update

Connection logon or logoff

Data Collector Updates
data collector updates server load cpu load example
Data Collector UpdatesServer load - CPU Load example
  • Data Collector

Server Load % :

Time

XenApp

5 minutes

data collector updates at logon time default load evaluator
Data Collector UpdatesAt Logon time - Default load evaluator

WI/XML

Data Collector

Server A

Ctxnotif.dll

IMA

MFSrvSS.dll

Dynamic Store

LMSSS.DLL

X

IMA

BIAS

ICA Client

Server B

Server B

Server A

Server A

performance data helper api
The performance data helper interface calls the registry interface to retrieve performance data

Uses the PDH.DLL to access the PDH API

http://msdn2.microsoft.com/en-us/library/aa373083.aspx

Performance Data Helper – API
performance data helper c example
pdhStatus = PdhAddCounter ( hQuery,

"\\Processor(0)\\% Processor Time",

0,

&hCounter);

YOU MUST CALL THE PERFORMANCE COUNTER BY ITS NAME

Performance Data Helper – C++ Example
citrix and the pdh
\\Processor(_Total)\\% Processor Time

\\System\\Context Switches/sec

\\Memory\\% Committed Bytes In Use

\\Memory\\Page Faults/sec

\\Memory\\Pages/sec

\\PhysicalDisk(_Total)\\Disk Bytes/sec

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

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

Citrix and the PDH
performance data helper file system
English

Perfc009.dat

Perfh009.dat

German

Perfc007.dat

Perfh007.dat

Performance Data Helper – File system
citrix and the pdh17
Citrix and the PDH

We also provide Performance counters

citrix and the pdh18
HKLM\SYSTEM\CurrentControlSet\Services\IMAService\PerformanceHKLM\SYSTEM\CurrentControlSet\Services\IMAService\PerformanceCitrix and the PDH
black hole effect
Black hole effect

Problem

Solution

At Peak logon times a recently boot up server will get all connections and might become unresponsive

Cause: Server is unable to update the DC

Load Throttling

Intelligent load balancing

HKLM\SOFTWARE\Citrix\IMA\LMS\

(DWORD ) UseILB = 1

(DWORD ) ILBMultiplier = 2

before intelligent load biasing
Before Intelligent Load Biasing

Default BIAS = 10000/100 = 100

0 sessions

1 session

2 sessions

1 session comes

2nd session comes

Max Load (10000)

Max Load (10000)

Max Load (10000)

Current Load (200)

BIAS

Current Load (100)

BIAS

Current Load (0)

intelligent load biasing
Intelligent Load Biasing

Load = [(Max Load – Current Load) / ILBMultiplier] + Load

0 sessions

1 session

2 sessions

1 session comes

2nd session comes

Max Load (10000)

Max Load (10000)

Max Load (10000)

Current Load (7500)

ILBMultiplier (2)

BIAS

Current Load (5000)

ILBMultiplier (2)

BIAS

Current Load (0)

load throttling low logon rate
Load Throttling- Low logon rate

ICA Client

Data Collector

Server A

Dynamic Store

Server B

Server Load

BIAS

Server A

0

100

0

(10000-0)/2+0 = 5000

0

100

(10000-0)/2+0 = 5000

0

Server B

load throttling low logon rate24
Load Throttling- Low logon rate
  • Server load if Low logon rate
load throttling black hole effect
Load Throttling- Black hole effect

ICA Client

Data Collector

Server A

Dynamic Store

Server B

Server Load

BIAS

Server A

0

(10000-0)/2+0 = 5000

(10000-7500)/2+7500 = 8750

0

(10000-5000)/2+5000 = 7500

6000

(10000-6000)/2+6000 = 8000

0

Server B

load throttling
Load Throttling
  • Server load at Peak logon times
upgrade to w2k3 causes full load
Upgrade to W2K3 causes full load

Problem

Solution

English W2K

\\System\\% Total Processor Time

English W2K3

\\Processor(_Total)\\% Processor Time

In W2K3, use

\\Processor(_Total)\\% Processor Time

some servers get all the connections
Some servers get all the connections

Problem

Solution

  • 1 server all the connections

Cause: Fail to read performance counters causes Load = 0

Fail to read performance counters causes Load = 10000

full load after installing an mui
Full load after installing an MUI

Problem

Solution

  • After installing MUI with advance load evaluators it results in load = 10000

Cause:

-> perfc007.dat (German) perfc009.dat (English)

HKLM\Software\Citrix\IMA\LMS\

EnableTranslation=1 (dword)

full load after installing an mui30
Jesús González

in a German restaurant

English Menu (perfc009.dat)

22 . Vegetable Soup

German Menu (perfc007.dat)

22. Gemüsensuppe

Full load after installing an MUI
troubleshooting32
Troubleshooting

Data Collector DC

LmsSS.dll

Full Load

LMS20Rules.dll

PDH.dll

XXXXXXXXXXXXXXXX

\\Processor(_Total)\\% Processor Time

troubleshooting failing to read performance counters full load
TroubleshootingFailing to read performance counters => full load
  • Use procmon (filemon) while restarting IMA
    • Make sure the correct perfcXXX.dat file can be accessed.
  • Consider rebuilding performance counters
    • http://support.microsoft.com/kb/300956/en-us
  • Check that no performance counter are disabled
  • [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\PerfDisk\Performance]
    • "Disable Performance Counters"=dword:00000001
  • Use CDFControl to gather CDF traces
    • http://support.citrix.com/article/CTX111961
slide34
LMSRuleDll_Interface::CreatePDHQuery() ERROR!!!!! rc = -1073738823

-1073738823 -> FFFFFFFFC0000BB9 (HEX)

http://msdn2.microsoft.com/en-us/library/aa373046.aspx

“The specified counter could not be found”

TroubleshootingCDF Traces example

summary
Deep understanding of load balancing

BIAS, PDH…

Understanding Intelligent load balancing

Load Throttling

Typical scenarios

Full load versus 0 load, MUI…

Troubleshooting techniques

So far we are able to resolve all the problems that arrive to EMEA tech support with those tips

Summary
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