After the completion of the business blue printing phase and before starting SAP Spend Performance Management (SPM) implementation, hardware sizing is highly recommended. The official Quick Sizer project for SPM helps you to determine the right hardware sizing. Refer to note 1253768 for further explanation of the usage of Quick Sizer tool.
Before using tool, it will help to do some groundwork and find data volumes for Transaction and Master Data. Make sure that you take into account multiple source systems, external data feeds like bank feeds for expenses etc based on the business scenario. The time frame for extracting the data should also be considered based on feedback from Business User. For example last five years or 2008 to current date etc.. Based on the industry segment/type of business, an appropriate time frame can be chosen. Best practice recommendation is to go back to the point of relevance for Analyzing Spend and avoid "data overloading". An example is that Freight spend which is heavily impacted by oil prices, suffers lot of volatility which is not necessarily predictable, hence a timeframe going back only a couple of years might suffice. Following is the list of information that needs to be made available to be able to use the SPM quicksizer.
1) Number of Invoice Lines
2) Number of pCard and T&E expense lines
3) Number of Contract Lines
4) Number of Scheduling Agreement Lines
5) Number of Purchase Order Lines
6) Number of Delivery Lines
7) Number of Budgeting and Forecasting Lines
8) Number of Project Lines
9) Number of lines for commodity/market pricing information
Master Data information:
1) Number of Item/Products
2) Number of Categories
3) Number of Suppliers
4) Number of Buyers
5) Number of Buying Organizations
6) Number of Cost Centers
7) Number of GL Accounts
8) Number of Site/Plants
9) Number of Management Orgs
The above list represents majority of the sizing volume inputs that would be required. Remember to inflate the above numbers appropriately in order to be able to accommodate for future loads until the next hardware upgrade is planned. In addition, consider the number of concurrent users productively using the SPM application. Now, armed with the above information, log into the SPM quicksizer tool and follow the instructions of the note 1253768 to get the recommended hardware specifications. For more information on how to use/understand the quicksizer tool check out the following blog links, Efficient SAP Hardware Sizing: Quick Sizer and Quick Sizer - Getting started.
Typically, SPM can be deployed either on an existing BW instance (which includes other analytics) or in a standalone setting where it doesn't compete for system resources. Both are valid deployment scenarios. The second scenario is straight forward, all you need to do is take the recommendations from the Quicksizer tool, validate them with the system administrators and commission the machine. In the first scenario, the hardware sizing results can be used to extend the existing resource allocations. The disk space is additive to the existing configuration, but the SAPs and RAM might not be, especially if the business users of the other analytics (that SPM shares the box with) do not have the same work hours. Remember it's the concurrent usage that typically drives RAM and SAPs numbers.
(Remember, additional information can be found at the SPM doc location in Service Market Place, link)