The IOCDS

This section provides some necessary information about the IOCDS and how to customize some settings for sharing network cards or DASDs among several LPARs. In the IOCDS, the chpid and types of the devices connected to the IBM System z are defined. The resources can be dedicated or shared among LPARs.

	Sharing Devices (DASD)
Do not share writable DASD among LPARs because this might result in data loss. Consider the definition of the necessary resources in advance when planning the setup for SUSE Linux Enterprise Server on IBM System z.

This example shows how to dedicate a DASD to one specific LPAR. This LPAR is referred to as LPAR1.

CHPID PATH=FD,TYPE=DSD,SHARED 
CNTLUNIT CUNUMBR=FD00,PATH=FD,UNITADD=((00,256)),UNIT=3990-2 
IODEVICE ADDRESS=(FD03,1),CUNUMBR=FD00,UNIT=3390,PART=LPAR1

To share a DASD among LPARs, delete the PART=LPAR1 part in the IOCDS definition. This might be useful for high availability reasons or for sharing data among LPARs read-only.

Several Linux systems can use the same network device if you share it among LPARs or z/VM guests. This reduces the number of network devices that must be provided to the Linux system. On the other hand, you might provide more than one network device to one Linux system to make it more available in case one connection fails.

Network cards like OSA-Express can be used in two different modes. These modes are known as QDIO and non-QDIO mode. Define these modes in the IOCDS by using the TYPE statement. QDIO mode is much faster than non-QDIO mode, but uses three device addresses instead of two in non-QDIO. Consider the limited number of device addresses when planning the setup of your IBM System z Linux environment.

CHPID PATH=(FE),SHARED,PARTITION=((LPAR1,LPAR2)),TYPE=OSE 
CNTLUNIT CUNUMBR=FE00,PATH=(FE),UNIT=OSA 
IODEVICE ADDRESS=(FE00,016),CUNUMBR=(FE00),UNIT=OSA 
IODEVICE ADDRESS=(FE00,016),CUNUMBR=(FE00),UNIT=OSA 
IODEVICE ADDRESS=(FEFE,001),CUNUMBR=(FE00),UNIT=OSAD

CHPID PATH=(FE),SHARED,PARTITION=((LPAR1,LPAR2)),TYPE=OSD 
CNTLUNIT CUNUMBER=FE00,PATH=(FE),UNIT=OSA 
IODEVICE ADDRESS=(FE00,016),CUNUMBR=(FE00),UNIT=OSA 
IODEVICE ADDRESS=(FEFE,001),CUNUMBR=(FE00),UNIT=OSAD