Sizing guide for SAP HANA


Sizing the RAM needed

Sizing an SAP HANA system is mainly based on the amount of data to be loaded into the SAP HANA database, because this determines the amount of main memory (or RAM) needed in an SAP HANA system. To size the RAM, the following steps have to be performed:

1. Determine the information that has to be transferred (either by replication or extraction) to the SAP HANA database. Note that typically customers will only select a sub-set of information from their ERP or CRM database, so this has to be done at the table level.
The sizing methodology is based on uncompressed source data size, so in case compression is used in the source database, this has to be taken into account as well. The information required for this step can be acquired with database tools. SAP Note 1514966 contains a script supporting this process for several database systems, for example, DB2 LUW and Oracle.
The current size of all the tables (without DB indexes) storing the required information in the source database is denoted as A.

2. Although the compression ratio achieved by SAP HANA can vary depending on the
data distribution, a working assumption is that, in general, a compression factor of 7 can be achieved:
B = ( A / 7 )
B is the amount of RAM required to store the data in the SAP HANA database.

3. Only 50% of the total RAM should be used for the in-memory database. The other 50% is
needed for temporary objects (for example, intermediate results), the operating system,
and application code:
C = B * 2
C is the total amount of RAM required.

The total amount of RAM should be rounded up to the next T-shirt configuration size, as
described in previous post , “T-shirt sizes for SAP HANA”   T-shirt Sizes, to get the correct T-shirt size needed.


Sizing the disks


The capacity of the disks is based on the total amount of RAM.
As described in  Hana Data persistence post, there are two types of storage in SAP HANA:

- Disk persistence
The persistence layer writes snapshots of the database in HANA to disk in regular intervals.
These are usually written to an array of SAS drives.

The capacity for this  storage is calculated based on the total amount of RAM:

Disk persistence = 4 * C

- Disk log
This contains the database logs, written to flash technology storage devices, that is, SSDs
or PCIe Flash adapters.
The capacity for this storage is calculated based on the total amount of RAM:

Disklog = 1 * C

The certified hardware configurations already take these rules into account, so there is no
need to perform this disk sizing.



Sizing the CPUs

A CPU sizing only has to be performed in addition to the memory sizing if a massive amount of users working on a relatively small amount of data is expected. Choose the T-shirt configuration size that satisfies both the memory and CPU requirements.
The CPU sizing is user-based. The SAP HANA system has to support 300 SAPS for each concurrently active user. The servers used for the IBM Systems Solution for SAP HANA support about 60 - 65 concurrently active users per CPU, depending on the server model.


Selecting a T-shirt size

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, a sizing result of 400 GB for the main memory (C) suggests a T-shirt size of M.
The sizing methodology described above is valid for SAP HANA in a side-car approach.
Other use cases might require another sizing methodology, for example, for SAP HANA as the database for an SAP BW system. Also, SAP HANA is constantly being optimized, which might affect the sizing methodology. Consult SAP documentation regarding other use cases and up-to-date sizing information.


Note: The sizing approach described here is simplified and can only provide a rough idea of the sizing process for the actual sizing for SAP HANA. Consult the SAP sizing documentation for SAP HANA when performing an actual sizing.


In addition to the sizing methodologies described in SAP Notes, SAP provides sizing support
for SAP HANA in SAP Quick Sizer. SAP Quick Sizer is an online sizing tool that supports most of the SAP solutions available. For SAP HANA it supports sizing for these:

  • Standalone SAP HANA system, implementing the sizing algorithms described in SAP Note 1514966 (which we described above)   
  • SAP HANA as the database for a SAP BW system, implementing the sizing algorithms described in SAP Note 1637145
  • Special sizing support for the SAP HANA Rapid Deployment solutions

The SAP Quick Sizer is accessible online at:

http://service.sap.com/quicksizer


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