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How many server nodes can you create per instance

Former Member
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Hi,

Very often the bottle neck in a java installation (NW04s) is the heap size. In order to increase the heap you simple create new server nodes.

My question is:

How many server nodes can you create per instance?

Is there an upper limit before you have to create a new dialog instance (with a web dispatcher)?

I can imagine that when you create a new server node you also have to increase the heap and max therad of the dispatcher. Is there any upper limit of the heap size of the dispatcher node ?

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Answers (5)

Answers (5)

cathal_ohare
Employee
Employee
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Hi All,

Officially there is no limit to the amount of server nodes you can add, If you have available the memory and cpu you can keep adding server nodes.

Manish point #2 above though is relevant when adding more nodes. From experiance I would a maximum 5 or 6 nodes, after this you may want to consider adding a Dialog instance on another host.

Kind regards,

Cathal

Former Member
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Hello.

The limit is 16 servers per node, because of the ports used by the server/dispatcher as indicated here:

http://help.sap.com/saphelp_nw70ehp1/helpdata/en/a2/f9d7fed2adc340ab462ae159d19509/content.htm

former_member906139
Active Participant
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Hello,

Calculation for number of server nodes goes like this,

No. of server Node = (RAM you want to assign or available RAM in GB)/2.5 ============> for 64-bit system

No. of server Node = (RAM you want to assign or available RAM in GB)/1.5 ============> for 32-bit system

Hence as per above discussion, we should go with 5 server nodes means,

5 = RAM/2.5 ( Assuming you are on 64-bit platform)

i.e. RAM = 12.5 GB.

Also this depends upon what all usage types you are using in your system.

If you want all usage types should be in system i.e. AS JAVA, EPC, EP, BI and DI ( PI is not included), then it will be good if you use system with 16GB RAM and five server nodes.

Please also update if you are now with more info, so that all of us gets update.

Regards,

Abhay

Former Member
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Thanks for your input

In theory the only limit, of how many server nodes you can create, should be memory/disk/cpu

BUT

I have seen different recommendation about how many server nodes you should create before you create a new dialog-instance. Thereof my question:

How many server-nodes should you create before creating a dialog-instance?

Manoj

The heap configuration is set by note recommendation: 1008311 (since we are running on AIX/IBM JDK)

Heap configuration is:

-Xms2048M

-Xmn1000M

Former Member
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Rasmus , I think you laid out a real good scenario for every one to contribute

I may be very late but just updating this forum for benefit of everyone who visits this.

In addition to all the points above one must also consider following things if one decides to add more server nodes to one dispatcher

1.Garbage collection time

2.Dispatcher would keep on sending request to node S2 if it is not completely bad and there by impacting all the servernode so you might end up restartiing the entire cluster.

3,Debugging also becomes diffculy as you are not sure on which server node you are within the cluster.

4.If you have something like F5 which does hear beat monitoring even one server node goes bad F5 will not report anything.

So in my view one server node per dispatcher is an ideal configuration.

Over All Dispatcher does not consume more resouces (Disk Space + CPU + memory ) at the same time it will give you maintenance flexibility.

Nothing is right or wrong ,all these things are based on how your infrastructure set up is.

Cheers !!

Manish Jain

Former Member
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Quoted as:

Proper number of server nodes within an instance:

u2013 Configure JVM heap according to Note 723909

u2013 #ServerNodes = availableMemory / (JavaHeapPermSpaceStack)

Please refer to [http://service.sap.com/performance|http://service.sap.com/performance]

Former Member
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I believe you can add upto 16 nodes but make sure you have enough resources (e.g. memory)

Former Member
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Thanks for your replyes !

The note 723909 tells you just how to configure the heap but is not telling you how many server nodes you can create.

In the following guideline by SAP:

"How to Performance Optimize SAP GRC Access Control 5.3" (GRC is running on a NW04 JAVA stack)

the guideline says:

"Do not configure more than 5 server nodes per Java instance. Rather add a dialog instance in addition to your central instance."

So insted of 16 server nodes the guide line says you should only create 5 server nodes.

16 server nodes is a number that circulates at SAP courses around the world.

Hence there is different number circulating around

So back to the question:

If you have an unlimited amount of resources

How many server nodes can you create or is optimal for an instance?

Former Member
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If you have an unlimited amount of resources

Is this possible?

How many server nodes can you create or is optimal for an instance?

Are you having performance problems? How many CPU's you have? Did you monitor the threads? Did you tune any exisiting parameters? Consider adding nodes only if there is perfromance problems. You may think of adding one node/processor to start with.

Hope this helps.

Manoj

Former Member
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Is this possible?

The CPU is not the problem (the CPU load is low). If we want we could add TB of memory. The limit in this case is the heapsize. The uper limit of the heap is 2048MB and then you have to create new servernodes.

The problem with the heap is that:

-Ratio of full garbage collections is high

-Garbage Collection Time is high

-The fill grade of the heap is high

Hence the heap is the problem here!

Moreover it is a bigg differens between 5 and 16 servernodes.

Former Member
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Did you try to increase initial heap size (Xms) parameter? This decides the frequency of garbage collection cycle, amount of heap growth before new cycle starts. Too many GCs consumes CPU so you have to fine tune.

hope this helps.

Manoj

sunny_pahuja2
Active Contributor
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Hi

> My question is:

>

> How many server nodes can you create per instance?

This depends upon your hardware size like RAM, CPU etc..

> Is there an upper limit before you have to create a new dialog instance (with a web dispatcher)?

> I can imagine that when you create a new server node you also have to increase the heap and max therad of the dispatcher. Is there any upper limit of the heap size of the dispatcher node ?

Check SAP Note 723909 - Java VM settings for J2EE 6.40/7.0

Thanks

Sunny

jorge_velasquez
Contributor
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Hi Sunny,

NW 7.3 SP 7.

I have 32 GB RAM and 8 CPU for my EP CI server and the same for my Dialog Instance.

When I added another Server Node to the instance the Portal turn slow.

It does not makes sense but probably is because of JVM Settings that has to be adjusted.

Global Area: 1

InitialHeapSize 2048

MaxHeapSize 2048

MaxNewSize 410

MaxPermSize 1024

permSize 1024

I added in configtool  --- set value to 2-- save -- restart

Any Clue?