r14 - 2017-02-27 - 13:30:06 - PaulEllisYou are here: TWiki >  Deployment Web > DeploymentPlanningAndDesign > ProofOfConceptSizingIn6x

Proof of Concept Sizing when using Continuous Engineering capabilities in 6.x new.png

Authors: PaulEllis
Build basis: Collaborative Lifecycle Management 6.x; aka IoT Solution for Continuous Engineering 6.x

This article intends to only discuss the limited use cases of a Proof of Concept, and installations of 1-20 users, which we see exhibit similar patterns and anti-patterns in terms of deployment. In general, a proof of concept is usually synonymous with an evaluation. However, where proof of concepts are to include real data as part of the evaluation, then thought must be given to the topology from the very start. There are excellent articles within this wiki on topologies for larger sizes, as well as the blog post Getting to a right-sized Jazz environment, which also discusses sizing considerations, but some of those are outside the scope of this page.
With the introduction of advanced configuration management features in CLM 6.x, the Standard Topologies now require more hardware than in releases prior to 6.x. If the intention is to use the configuration management capabilities within Rational DOORS Next Generation and/or Rational Quality Manager then you need to adhere to the following guidelines.

Why is a single-server topology no longer adequate for a Proof of Concept (PoC)?

As documented in the Evaluation topology, this was described as "The evaluation topology does not meet the demands of a typical production workload because of the limited scalability of the single application server. While this topology is ideal for evaluations, demonstrations, and training purposes realize that the data created in an evaluation topology cannot be transferred to a scalable production environment when the evaluation is complete."
The full list of applications within the CLM suite, prior to the 6.x release stream was documented as an Evaluation topology using Windows/Tomcat : RTC, RQM, RDNG, DM, JTS, JRS, LQE, DCC, RELM and VVC, with the CLMHelp, RM converter and admin applications all added too. This does not even consider a reverse proxy setup, which quite often is added for when the future expansion into an Enterprise Topology occurs.

The inclusion of configuration management capabilities in 6.x added a Link Index Provider (LDX) and a Global Configuration Management (GCM) application. This meant that if you were utilizing all of the CLM applications, then there would be even more pressure on the server during key moments of operation. Indeed, some experienced server strain when using the Evaluation Topology in 5.x too when DCC (Data Collection Component) and the Data Warehouse were collocated with the CLM applications.
This situation is acerbated in 6.x with the inclusion of the Lifecycle Query Engine (LQE) now being utilized by more than just RELM (Rational Engineering Lifeycle Manager) and Design Manager. The main stream use and it's fairly constant updates (to provide near real-time reporting) necessitate some thought on how to deploy, even a simple setup.

The Evaluation topology was intended to be just that. A small setup to trial features of the CLM suite, downloaded from jazz.net. In 2016, this is better served by using the jazz.net sandbox, or doorsng.com for learning about new features, but if a SaaS (Software as a Service) or aaMS (as a Managed Service) option is not appropriate for you, then a small on-premise setup should continue as detailed below.

How ONE expensive scenario can cause your PoC server serious harm

The sizing of a small setup is the same for 1 user as it is 10, or even 20. In many ways, your number of users are unlikely to be a major consideration during your Proof of Concept phase, or indeed if you're a deploying to a small number of users. The capabilities you wish to avail of and the data which you work with will have a much more fundamental impact on your decisions than a relatively small number of users.
There is an entire section of this wiki dedicated to monitoring and another to performance, but I have attempted to summarize below the cross-cutting considerations in this one article.

Considerations for RAM, CPU and disk Input/Output

When calculating a maximum server sizing, the first place we recommend perusing is the Performance Datasheets and Sizing Guidelines, along with the Sizing Strategy for 6.x and then probably add in additional information per application, for example, DNG Sizing Guide for 6.x.
As it is not our recommendation to collocate all of our applications on one server in a production environment, there is minimal performance testing done at this level.
In terms of the most fundamental sizing advice, we have always advocated that the database server (if not Derby) be located on its own server. Oracle, DB2 and SQL Server will directly compete for the key 3 resources and unless they're plentiful, problems will occur in an intermittent and unpredictable manner. Essentially, if you're using not using the Derby database, you're not in a Proof of Concept mode and must upgrade expectations along with the scale of your middleware!
The Lifecycle Query Engine, whilst not new to 6.x has been adopted by the newly configuration managed applications and should only be installed if you're intending to use this in DM, RDNG or RQM. This application, like RDNG, is using a file based Jena index for its triple stores and is particularly RAM and I/O intensive as it grows. The importance of this to the overall ability to run in a single server is highlighted in the Lifecycle Query Engine Best Practises article.
If you're at the point of splitting now into a 2-application-server topology for evaluation, you should consider that along with the LQE, the Data Collection Component, and the Reporting Service (also known as JRS) would also benefit from being separated from the main applications.
In terms of RAM, CPU and Input/Output then these 3 rules apply, especially when RDNG and LQE are being considered:

  1. Add processors to support more concurrent users
  2. Add faster disks to support more data
  3. Add memory to support more data (and more concurrent users)

Why is the data more important than the number of users?

When calculating the minimum sizing, then there isn't the same information available, but as you can see from DNG recommended hardware settings, the point in the graph for 1 user really depends on the data that is in use. If you are testing RDNG using data from your current system, say DOORS 9, then you may use the migration utility to import 10,000 objects across for the PoC. You may have several groups who want to work with their data, so multiple modules of 10,000 objects. As you can see you will soon climb the vertical access, even before you have unleashed your full use base.
In Tim Feeney's page CLM Expensive Scenarios we can see why data might be more important across more than RDNG. Each application lists its Achilles heel(s) to show where data is going to be a significant factor in your sizing decision.
These expensive scenarios again have largely been experienced during peak times on enterprise servers, however the guide is an essential list for your CLM Administrator to reference, if they are trying to explain a degrading system in terms of performance and/or reliability.

The silver bullet of using Java Heap for better performance

One of the common misconceptions that we see, especially with PoC setups is that the Java heap size (the Xmx, Xms, and Xmn) settings in your webserver are often overset.
In the use case we are discussing, the most useful equation to consider is quite simply:


RAM > Java Heap + OS needs + Jena indices (from LQE and RDNG) 
                           + native memory requirements for so many applications 
                           + 1GB for DirectByteBuffers (the value of "-XXMaxDirectMemorySize" JVM argument)

Therefore, using all of the available RAM for the Java heap is not going to be the silver bullet for performance that you would perhaps otherwise infer from our guidance elsewhere, where we are considering a single application, like RDNG, per server. The most appropriate setting for the heap is usually 50% of RAM and then use Garbage Collection to tune up, or down if you see Native Memory errors. See below for more on Native Memory errors.
Before I move on to monitoring the system, I want to make a delineation on Garbage Collection. It is important to know how much RAM, CPU etc you have on your server. It may be important to see the contents of the Javacore at the time of any crash, but what IBM Support need to see more than anything for a performance issue for these use cases is the verboseGC log!
Point 4 of Must Gather Information describes how to set this. The overhead is minimal however the information is invaluable. In most cases of performance and instability issues I have seen on small server installations, it is this log that allows me to get to root cause faster and tune more effectively than any other tool.

Monitor your way to good Java health

Tuning the Java heap is outside of the scope of this topic, but below are some links for further reading. In essence though, you should let data make decisions for you without the panic of a system-down situation, or guesstimates based on load.
WebSphere Liberty has a very simple Admin tool which will allow you to see how the CPU, RAM and threads are performing, which is available with any web server through Java Management Extensions (JMX). The simplest guide to setting this up is, Monitor your server with JMX, which you no longer need to uncomment and restart the application server.
To then access this information, use JConsole, which is part of the RTC client and documented here.
A false positive we have seen on Windows is when we see Competition for the 4GB Windows memory space. This is nothing new, but we have seen LQE in particular, when collocated with the other applications encounter this problem. As described in the link, you can move to uncompressedrefs to resolve this, but in doing so you're increasing the RAM requirements...just to note.


Non functional testing and small servers

If you intend to perform non functional testing on a server then we have written two articles on how we perform this and also what you need to tune in order to allow the simulation not to encounter unrelated issues to the tests being performed.


Conclusion

I imagine that having read all the advice above, many people just want to see a minimum specification laid out in a simple table. With all the caveats detailed above, and indeed in the related articles, we're recommending.

It is possible to load all of the applications on 1 machine of around 16GB RAM and 4vCPU (my old laptop), it just isn't advisable and it isn't going to be stable. In essence you're going to spend a lot of time unnecessarily chasing phantoms and creating a poor perception for your users.
We would therefore strongly recommend that if you are evaluating all of the applications for a Proof of Concept, or indeed initially for a small set of users with aspirations to trial the additional applications/features and then roll out further capabilities, then you should start with (my new laptop):

1 x [32 GB, 8 vCPU and fast disk (SSD)* - non-reporting applications]
1 x [32 GB, 8 vCPU and fast disk (SSD)** - reporting applications]
1 x [Separate DB Server - 12GB RAM, 4 vCPU]
*SSD is required if RDNG is to be used
**SSD is essential if LQE is in use with configuration management enabled projects in RM and/or RQM


Lifecycle Query Engine Sizing is the definitive guide for sizing of the LQE machine. The advice, even in this conclusion once again reiterates the opening paragraph where it needs to be stated that any proof of concept that makes extensive use of real data should evaluate the needs and not assume that evaluation is based on just the number of users.
There is an article from 2014 for basic DCC guidance: Performance summary and guidance for the Data Collection Component in Rational Reporting for Development Intelligence

Related topics: Deployment web home, Deployment web home

External links:

Additional contributors: TimFeeney, StevenBeard

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