IBM Z® compatible disk layout

Red Hat Enterprise Linux 8.6 LPAR mode z/VM guest KVM guest

With the compatible disk layout a DASD can have up to three partitions that can be accessed by traditional mainframe operating systems.

You can only format ECKD type DASD with the compatible disk layout.

Figure 1 illustrates a DASD with the compatible disk layout.

Figure 1. Compatible disk layout
The graphic shows this order: first IPL record, second VOL1, third VTOC, then up to three partitions

The IPL records, volume label (VOL1), and VTOC of disks with the compatible disk layout are on the first two tracks of the disks. These tracks are not intended for use by Linux® applications. Using the tracks can result in data loss.

Linux can address the device as a whole as /dev/dasd<x>, where <x> can be one to four letters that identify the individual DASD.

Disks with the compatible disk layout can have one to three partitions. Linux addresses the first partition as /dev/dasd<x>1, the second as /dev/dasd<x>2, and the third as /dev/dasd<x>3.

You use the dasdfmt command to format a disk with the compatible disk layout. You use the fdasd command to create and modify partitions.