Level: Intermediate George Demetriou, Performance Engineer, Iris Associates
02 Aug 1999 This article describes performance analysis of Domino Web server resource utilization on Windows NT. The test shows the impact of changing the HTTP threads setting on both server response time and resource utilization.
So, you've got your Domino server all set up to "work the Web," but want to make sure that you get the most out of the system? You may not realize that you can adjust the number of HTTP threads running on your server, and improve both the server's response time and resource utilization.
In this article, we'll take an
in-depth look at a performance analysis of Domino Web server
resource utilization on Windows NT. The test shows the impact of
changing the HTTP threads setting on server performance. We'll
start by defining what HTTP threads are, then describe the test
methodology and test data, and finally summarize what the results
mean to you. This can help you decide how you want to set up your
environment in the future.
For background information on how we
conduct performance analyses here at Lotus/Iris, or an introduction
to the tools we use, see "Optimizing server performance: Port encryption & Buffer Pool settings." To read
more recommendations for improving server performance, see the
"Top 10 ways you can improve server performance."
What are HTTP
threads?
HTTP threads are threads of execution
for handling incoming HTTP requests. To specify the number of
threads that you want active on your Domino server, use the "Number
of active threads" field in the HTTP section of the Server document
in the Public Address Book. The default setting is 40. When the
HTTP server task initializes on the Domino server, the defined
threads are created and occupy approximately 20-40Kb of memory
each. These threads are fixed in number until you change the value
in the Server document, and then restart the HTTP task.
Our expectation for this performance
analysis of a Domino server functioning as an HTTP-based messaging
server was that the HTTP active threads setting should be equal to
the number of Web users on a particular Domino server. For example,
if you are anticipating 200 Web users to use a Domino server, you
might assume that you should set the HTTP active threads to 200.
However, as you will see from our test results, this is
not the case.
Test methodology and test data
To run the test scenarios, we set up
one client that could simulate Web browser users running the
new NotesBench
WebMail workload with the following
configuration:
- CPUs: One Pentium II
processor
- Memory: 256MB RAM
- OS: Windows NT 4.0
Workstation
- Notes: Release 5 (based on Beta
1)
- NotesBench WebMail workload
(available with Release 5 of NotesBench)
We set up a Domino server with the
following configuration:
- CPUs: Two Intel Pentium II/300MHz
with 512K Level 2 Cache
- Memory: 512MB RAM
- Single SCSI controller
- Three hardware arrays created
across six disk drives
- Hard Drives:
--Logical C: One RAID0 7200rpm drive for OS
--Logical D: One RAID0 7200rpm drive for page file and Domino
executables
--Logical F: One RAID5 7200rpm with four drives for user mail
files, logs, and mail.box (total 36GB storage for \data
directory)
- OS: Windows NT Server 4.0, Service
Pack 3
- Domino: Release 4.62 for Windows
NT
In particular, we wanted to test the
relative impact (the number of users, the response time, and the
resource utilization) when varying the following HTTP threads
settings: 10, 25, 50, 100, and 200. We applied each setting to a
NotesBench WebMail multirun test with 25, 50, 100, and 200 users.
This test scenario compared average user response times, probe
response time, system CPU utilization, memory used, and disk
utilization at various loads. We ran each test for approximately 60
minutes in a steady state, with a ramp-up period of 5
minutes.
The workload we used for all the
tests is the new NotesBench WebMail workload, which will be
available when R5 ships. This workload enables each simulated user
to access their respective mail file, built using the R4.6 Mail -
Combined template (mailc46.ntf), via the HTTP protocol. Each user
iteratively executes a 15-minute script that consists
of:
- Preparing and sending a 10K message
to three recipients dynamically selected from the server's
directory every 15 minutes.
- Reading the Inbox and the first
five Inbox documents, and deleting the first message.
All messages are sent to and received
by other simulated WebMail users on the same Domino server.
In addition, the WebMail workload
requires the following NOTES.INI settings on the client:
- ThreadStagger = 5
(seconds)
- NormalMessageSize=10000
- NumMessageRecipients=3
The ThreadStagger setting specifies
when each user logon begins, so in this case, each user logon
begins at five seconds apart. This setting helps the server ramp up
smoothly, without having connection timeouts during the ramp-up
phase. The NormalMessageSize and NumMessageRecipients settings
specify the size of the message (10K) and the number of recipients
(three) that are used in the 15-minute WebMail script.
To see the results of these tests,
see the sidebar "HTTP Threads Settings Test Results." For our conclusions,
see the following section, "What did we find out?"
What did we find out?
Our basic discovery was that
more HTTP threads is NOT necessarily
better. In fact, as indicated by the data and graphs, there is a
degradation in performance and an increase in memory consumption,
if there are more HTTP threads defined
than are needed. Therefore,
you should only define the minimum number of HTTP threads necessary
for your server's load.
The best way to determine the
optimal HTTP threads setting for a given user load is to first run
with the HTTP threads setting approximately equal to the user load.
Then, at the server console, check the peak number of HTTP threads
used by typing the following:
show statistic
domino.threads.active.peak
Since this value indicates the
maximum number of HTTP threads in use, it is much more appropriate
to use this value for the HTTP threads setting in the Server
document.
If you've just installed a Domino
server and you have a general idea of how many Web mail users it
will be supporting, then a good starting value for the number of
HTTP threads setting is 10% of the number of Web users. For
example, if you anticipate 200 Web mail users, a suitable initial
setting for the HTTP threads is 20. Once you have your users
running, you can "fine tune" the setting based on the
"domino.threads.active.peak" statistic. If you constantly see that
the Peak value is the same as the value you defined, you should
increase the value of defined threads in the HTTP section of your
Server document.
What if you don't use your server
for HTTP-based messaging? You can still monitor the
"domino.threads.active.peak" statistic to determine if you've
started more threads than you need. By reducing the number of
threads, you can decrease the amount of memory used by the HTTP
server and this memory will be available for other activity on the
server.
Resources
About the author  | | | George Demetriou started working at
Iris in 1997 from Eastman Software. He is a Performance Engineer
who has spent his time working on Domino Web server performance
measurement and evaluation. |
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