Linux disks and partition names may be different from other operating systems. You need to know the names that Linux uses when you create and mount partitions. Here's the basic naming scheme:
The DASD devices are named /dev/dasd/xxxx/device where xxxx is the device number in hexadecimal notation. The kernel that ships with Debian GNU/Linux uses devfs so the device nodes are created and removed automatically when DASD are attached or detached. Please see chapter 3 in Device Drivers and Installation Commands for more information about this.
S/390 disk partitions allow for 3 separate partitions. They are called /dev/dasd/xxxx/part1, /dev/dasd/xxxx/part2 and /dev/dasd/xxxx/part3.