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Specific Features and Behaviors of Exchange Load Generator

 

Topic Last Modified: 2007-01-18

This topic contains in-depth observations about some specific features and behaviors of Exchange Load Generator.

Exchange Load Generator has two public folder tasks: Public Folder Post and Browse Public Folder. Both tasks will choose any public folder in the MAPI TLH (the default public folder root), except for one named Internet Newsgroups.

Exchange Load Generator can choose other folders to browse or post, even if it did not create them. Therefore, in such an attempt, Exchange Load Generator may not always run some tasks and indicate it had access denied. We recommend that you have only the public folders that were created by Exchange Load Generator.

When Exchange Load Generator creates its public folders, it changes the permissions to give owner rights as default. This means that any user can edit, delete, or add new posts. This is required for Exchange Load Generator to simulate multiple users when logging on to users using their respective accounts. If the permissions are changed in any way, Exchange Load Generator might not always create posts or browse the public folders.

A core functionality of Exchange Load Generator is that it can send mail to users, distribution groups, and query-based distribution groups. When you set up a complex topology, you must understand how Exchange Load Generator will decide who it will send mail to.

There are two distinct scenarios that cause Exchange Load Generator to send mail. The first is when Exchange Load Generator is processing the Inbox or browsing old mail and tries to Reply or Reply all to one or more messages. In this scenario, Exchange Load Generator sends the reply to the sender and recipients (if Reply all), regardless of whether the users are in the topology. This means that when a topology is initialized, all the mail that is populated in the mailbox is consistent with the topology settings of the client that initialized all mailboxes. As test runs occur, e-mail is added from clients that have their own topology configuration, which can be the same as the one that initialized the mail. If at any point there is a change in the topology (for example, a server is removed or users are added or removed), the mail that is already in the user’s mailboxes is not affected. If Exchange Load Generator tries to reply to a sender that no longer exists, a non-delivery report (NDR) occurs.

The other scenario is with regard to sending a new mail. When sending a new mail, Exchange Load Generator uses the information in the send mail task for selecting the number of recipients and whether distribution groups and query-based distribution groups should be added. After this step, Exchange Load Generator chooses the recipients based on the test group configuration. For example, if the topology settings are configured so that a server has 1,000 users and the test targets only 10 users, Exchange Load Generator will only consider 10 users as possible recipients. Additionally, the distribution groups and query-based distribution groups will be configured to the 1,000 users. Therefore any mail going to them will end up in users other than the 10 users.

To fine-tune stress, it helps to understand how Exchange Load Generator calculates how much load will occur against servers. This calculation process occurs in two steps.

In the first step, Exchange Load Generator calculates the number of tasks that need to run per user group. This is the sum of all task frequencies multiplied by the number of users.

In the second step, Exchange Load Generator sums the number of tasks of all the user groups that the client computer that the test is running on is configured to do. In other words, this is the result of the calculation from the first step. The summed task is spread across the total duration of the simulation. The duration values are set in the Specify test settings page in the user interface as follows:

  • The length of a 'simulation day' defined in hours, minutes, and seconds
  • The total length of the simulation defined as forever, or as a specified duration (in hours, minutes, and seconds)

For example, if there is one group that has 100 users and will run the Send Mail task 10 times in an eight-hour configuration, Exchange Load Generator will spread 1,000 tasks across eight hours, running each task every 347 milliseconds (1,000 divided by 8 hours).

Independently of the concurrency settings, the duration of the simulation will stop the test after a designated elapsed time is started. For the previous example, if the duration of the simulation was two or eight hours, the tasks would still run every 347 milliseconds. The difference is that the test would stop in two and eight hours, respectively.

Finally, there is an additional option: stress mode. In stress mode, Exchange Load Generator ignores the concurrency settings and task frequencies. It runs the tasks back-to-back and without a wait for the duration of the simulation. For example, if the duration of the simulation was set to eight hours, the tasks would run for eight hours without the 347 millisecond wait between them. Because only the client, server, and network configurations limit this mode, results will vary extensively from setup to setup. Therefore, we do not recommend this mode for comparing computers or for sizing.

Exchange Load Generator has two message sets for running simulation and they are configured in the LoadGenConfig.xml file. One set is for sending new messages and another set is for posting in public folders. The former is defined in the Send Mail task and it is also used by individual mailbox initialization. The latter is defined in the Public Folder Post task.

Exchange Load Generator has one message set for public store initialization. It is also configured in the LoadGenConfig.xml file.

You can use any MSG MAPI message that is formatted correctly with Exchange Load Generator. The following table lists the message mix of the files that are downloaded to the installation directory. The attachments can be documents, clip art, spreadsheets, or any type recognized by the client mail application.

Exchange Load Generator loads in memory all messages used from both message sets, per user group. This means that if you have multiple user groups, even if with the same list of messages to be used, they will be loaded separately and occupy more space in memory. Additionally, the overall memory consumption of Exchange Load Generator increases if many custom messages are used.

The following table lists the message mix of the files that are downloaded to the installation directory. Use these files as is, or customize for your test simulation.

 

File name Content type Size (in bytes) in DAV

msg00001

HTML

2187

msg00002

HTML

3858

msg00003

HTML

5174

msg00004

HTML

6716

msg00005

HTML

11639

msg00006

HTML

16720

msg00007

HTML

32518

msg00008

HTML

47781

msg00009

HTML

105244

msg00010

HTML

211710

msg00011

HTML

313025

msg00012

HTML

530583

msg00013

HTML

106890

msg00014

HTML

2651291

msg00015

HTML w/attachment

6831

msg00016

HTML w/attachment

7869

msg00017

HTML w/attachment

11965

msg00018

HTML w/attachment

18178

msg00019

HTML w/attachment

48299

msg00020

HTML w/attachment

416410

msg00021

HTML w/attachment

1053029

msg00022

RTF

6404

msg00023

RTF

8280

msg00024

RTF

10174

msg00025

RTF

20850

msg00026

RTF

30254

msg00027

RTF

61812

msg00028

RTF

92586

msg00029

RTF

205005

msg00030

RTF

409874

msg00031

RTF

614404

msg00032

RTF

1048846

msg00033

RTF w/attachment

12217

msg00034

RTF w/attachment

15326

msg00035

RTF w/attachment

20881

msg00036

RTF w/attachment

31032

msg00037

RTF w/attachment

61383

msg00038

RTF w/attachment

614192

msg00039

RTF w/attachment

1057303

msg00040

Text

1472

msg00041

Text

2287

msg00042

Text

2681

msg00043

Text

3190

msg00044

Text

4900

msg00045

Text

6624

msg00046

Text

11679

msg00047

Text

16607

msg00048

Text

35177

msg00049

Text

68834

msg00050

Text

102574

msg00051

Text

346338

msg00052

Text w/attachment

5661

msg00053

Text w/attachment

6849

msg00054

Text w/attachment

10779

msg00055

Text w/attachment

16521

msg00056

Text w/attachment

38678

msg00057

Text w/attachment

277239

msg00058

Text w/attachment

1051835

 
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