SAP HANA Sizing

Sizing is a usual term in SAP, which means determining the hardware requirements of an SAP System such as physical memory, CPU power, and I/O capacity.

The process of translating business requirements into hardware requirements 

is called hardware sizing.

The size of the hardware and database is influenced by both business aspects and technological aspects. This means that the number of users using the various application components and the data load they put on the network must be taken into account.

Determining sizing requirement ensures that customers purchase hardware as per their business need and also ensures lower cost and reduce TCO.

SAP provides number of tools and methodologies, how these hardware requirements can be determined. The most Perceptible tool is the "Quick Sizer." 

SAP HANA In-memory database sizing consists of 

1. Memory sizing for static data
2. Memory sizing for objects creating during run-time such as data load and query execution
3. Disk sizing
4. CPU sizing

Memory:
CPU:
Disk Size:

For the purpose of successful SAP HANA implementation, SAP has provided various guidelines and methods to calculate the correct hardware size.
We can use any of the below method:

1. SAP HANA sizing using the QuickSizer tool
2. SAP HANA sizing using the DB specific scripts
3. SAP HANA sizing using the ABAP report

Selecting a T-shirt sizes:

According to the sizing results, select a SAP HANA T-shirt size that satisfies the sizing requirements in terms of main memory, and possibly CPU capabilities.
For example
The SAP hardware partners provide configurations for SAP HANA according to one or more of these T-shirt sizes. Below table lists the T-shirt sizes for SAP HANA.



The three main KPIs used to size for SAP HANA is

1. Main memory (RAM) space,
2. CPU processing performance
3. Disk size.

While traditional sizing approaches focus on CPU performance, the main driver for SAP HANA sizing is memory. Because SAP HANA is a main memory database, essentially all business data (e.g., master and transactional data) resides in the main memory, which leads to a higher memory footprint compared to traditional databases. In addition to the main memory required for storing the business data, temporary memory space is needed to operate the database management system — to support complex queries or data that is needed for buffers and caches, for example.

Sizing for SAP HANA includes unique requirements for CPU processing performance. The CPU behaves differently with SAP HANA compared to traditional databases. The processing engine for SAP HANA is optimized to operate very complex queries at maximum speed, which means that many of these queries are processed internally and in parallel, and most of the data is stored in a column-based format. This architecture not only might lead to a higher CPU demand compared to traditional databases, it also requires planning for a lower average utilization to ensure that there is enough headroom for the database to process queries sufficiently fast.

An in-memory database still requires disk storage space — to preserve database information if the system shuts down, either intentionally or due to a power loss, for instance. Data changes in the database must be periodically copied to disk to ensure a full image of the business data on disk, and to preserve the current state of the database and all of the data entered in the persistence layer. In addition, a logging mechanism is required to log changes and enable system recovery. To accommodate these requirements, there always must be enough space on disk to save data and logs.

Static & Dynamic RAM:

Calculation of Static RAM Size:

Static RAM Size means the amount of RAM required to store the data in the SAP HANA database.

Assuming the compression factor as 7:

Calculation of Dynamic RAM Size:

Dynamic RAM is for additional main memory required for objects that are created dynamically 

when new data is loaded or queries are executed. SAP recommends to keep Dynamic RAM size same as Static RAM size.

Calculation of Total RAM Size

                           Table footprint of source database: 186348 MB = 182 GB

                                Assumption: Source DB Compressed by factor 1.8

                           RAM = Source data footprint*2/7=182 GB*2/7*1.8=94 GB

                                   Disk          = 94 GB*4=376 GB
                                     (persistence) 
                                  Disk         = 94 GB
                                        (log)         

Refer below snotes which will help you more understanding HANA Sizing.

2121330 - SAP BW on HANA Sizing Report

1637145 - SAP BW on HANA: Sizing SAP In-Memory Database

1736976 - Sizing Report for BW on HANA

1799449 - Sizing report ERP on SAP HANA database

2296290 - New Sizing Report for BW on HANA