[THIN] Re: KB: CTX114844 - Effects of Varying the Number of CPUs of a Citrix Presentation Server
- From: "Nick Smith" <nick@xxxxxxxxxxxxxxxxxx>
- To: <thin@xxxxxxxxxxxxx>
- Date: Mon, 8 Oct 2007 07:44:00 +0100
I think the number of cores in the table is wrong - 4 quads should be 16?
From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf Of
Jim Kenzig ThinHelp.com
Sent: 07 October 2007 16:49
To: THIN
Subject: [THIN] KB: CTX114844 - Effects of Varying the Number of CPUs of a
Citrix Presentation Server
CTX114844 - Effects of Varying the Number of CPUs of a Citrix Presentation
Server
This document was published at: http://support.citrix.com/article/CTX114844
Document ID: CTX114844, Created on: Oct 4, 2007, Updated: Oct 5, 2007
Products: Citrix Presentation Server 4.5 for Windows Server 2003 x64 Edition,
Citrix Presentation Server 4.5 for Windows Server 2003
Summary
The number of users that a Presentation Server can support depends on several
factors including:
* The server's hardware specifications
* The applications used (because of the applications' CPU and memory
requirements)
* The amount of user input being processed by the applications
* What is considered to be maximum desired resource usage on the server; for
example, 90% CPU usage or 80% memory usage?
This article discusses the increase in user capacity when CPUs with multiple
cores are added. First, the Citrix benchmarking test for user capacity, known
as ICAMark, is described.
Citrix ICAMark
Citrix ICAMark is an internal tool which is based on the Citrix Server Test Kit
(CSTK) and used by Citrix Engineering for benchmarking purposes to quantify the
optimal number of simulated client sessions that can be connected to a
Presentation Server with acceptable performance. Extending the number of
concurrent simulated users beyond the optimal results will cause a decrease in
performance and may impact end user experience.
The test simulates users constantly typing and performing actions in Microsoft
Excel, Microsoft Access, and Microsoft PowerPoint. Other applications can
utilize more or less memory and CPU than Microsoft Office and therefore could
produce different results. Note also that the simulated users in this test are
constantly typing into these applications and may be considered more "rigorous"
than normal users.
In this test, a step size, "number of users," is defined as 10. During the
course of the test, after the first 10 users are logged in, ICAMark launches
simulated user scripts on all 10 sessions. Each script opens Microsoft
PowerPoint and simulates the creation of a presentation, including copies and
deletion of slides, font changes and presentation viewing. Once the PowerPoint
phase is complete, PowerPoint is closed and Microsoft Access is opened. The
script then simulates the creation of an Access database, including a table,
query, and form, with data manipulation. Once the Access phase is complete, a
Microsoft Excel spreadsheet is created, data populated into the spreadsheet is
used to do number of calculations and charts.
Based on how long the scripts take to complete, an ICAMark score is calculated.
For this test, a score of 80 has been determined as the optimal load for a
server. This means that the server has enough additional CPU and memory
resources to handle spikes in performance. When the test iteration score drops
below 80, additional users added to the server consume more resources,
producing lower test scores and slower performance.
Number of CPUs Effect on User Capacity
The benchmark test was performed with the following:
Server:
Quad Quad-Core Processors - 3.0GHz Xeon with 8 MB L2 Cache
6x 73 GB 2.5" SAS 10K RPM
64 GB RAM
16 GB Page File
Citrix Presentation Server 4.5
Microsoft Windows Server 2003 64-bit
Microsoft Office 2003 Professional
Clients:
Intel XEON 2.8 GHz Processor
1 GB RAM
Citrix Program Neighborhood Version 10.0
Microsoft Windows Server 2003 32-bit
Tests were performed by keeping the hardware static and disabling processors on
the server.
The following results were collected:
# of CPUs
# of Cores
# of Simulated Users
% Performance Increase
1
2
202
N. A.
2
4
323
60%
4
8
417
29%
[http://support.citrix.com/article/html/images/CTX114844-1.gif]
Number of CPU Cores Effect on User Capacity
The results conclude that the performance of 8 CPU Cores enabled and 417
concurrent simulated users, is equivalent to the performance of 4 CPU Cores
enabled with 323 concurrent simulated users, which is equivalent to the
performance of 2 CPU Cores enabled with 202 concurrent simulated users.
Moving from a dual to a quad core system equates to a 60% increase in
performance while moving from a quad to an eight core system equates to only a
29% increase in performance. In other words, as CPU cores are added to the
server, the increase in performance of the operating system becomes less. As in
this scenario server scalability is not linear with the number of processors,
and drops off sharply between 4-8 CPU cores.
All tests were run on Windows Server 2003 64-bit. In this scenario a 32-bit
operating system would be limited by the amount of kernel memory available.
Similar testing was conducted using this scenario on a 32-bit operating system.
The results showed that the system was unable to scale beyond 200 users. This
architecture limitation with 32-bit was worked around by using 32-bit and
64-bit applications on a 64-bit operating system.
Note: When sizing Presentation Servers the number of actual users per server
varies based on the applications deployed.
More Information
See Advanced Concepts Guide - Citrix Presentation Server, Platinum
Edition<http://support.citrix.com/article/entry.jspa?entryID=14748> - for a
list of additional Advanced Concepts Guide articles.
--
Jim Kenzig
Microsoft MVP - Terminal Services
http://www.thinhelp.com
Citrix Technology Professional
Provision Networks VIP
CEO The Kenzig Group
http://www.kenzig.com
Blog: http://www.techblink.com
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