Disk Configuration

The following gives recommendations on how to distribute files to disks in an SAP environment to ensure database security. You should have at least 3 disks.

·        Locate at least each of the following components of your system on separate disk systems:

Ў        SAP database on a RAID5 system (or RAID0+1)

Ў        SAP transaction logs on a RAID1 system

Ў        Other files such as the Windows operating system, Windows page file, tempdb database and executables on a disk or RAID system

Use hardware RAID systems and not the software mirroring offered by the Windows disk manager.

·        Configure the system with two Windows operating systems. The second, auxiliary version is used to perform backup and restore operations with the Windows backup program.

Set the Windows option Automatically adjust clock for daylight saving times in the main Windows system, but not in the auxiliary system.

·        If your system has write back caches for hard disks and RAID controllers, switch these off. Otherwise, in the event of a power failure, the data in the cache could be permanently lost resulting in a corrupted database. In systems with a standby battery buffered cache, you may leave write caches on, if the manufacturer explicitly recommends this for databases.

Disk read caches should always be turned on for maximum performance.

The following table shows a minimal disk configuration for the SAP system running with a SQL Server Database. Note that the letters for the devices have been chosen to indicate their contents, for example, D: for SAP data.

Optionally, if you have the disk capacity available it would benefit the throughput of your system, if you place one or more of the following system components on separate disks. The distribution of files could then look like this:

P: The Windows page file

T: Files for the Tempdb

C: Files for the SQL Server, Windows and SAP executables

Example of Minimal ConfigurationTable

Folder

Disk

Files

C:\WINNT

1

Windows Operating System

C:\HELPNT

1

Auxiliary Windows version

C:\Program Files\Microsoft SQL Server

1

SQL Server executables, msdb and master databases

C:\TEMPDB

1

tempdb

C:\USR\SAP

1

SAP executables

C:\pagefile.sys

1

Windows page file

D:\<SID>DATA

2

SAP database, data files

L:\<SID>LOG

3

SAP database log files

For the sake of clarity, this documentation refers to the disks of the example configuration as follows:

Disk 1

Executables disk

RAID1 disk system

Disk 2

SAP data disk

RAID5 disk system

Disk 3

SAP log disk

RAID1 disk system

See also:

Distribution of Files to Disk