26.1. Tuning Linux guests under VM

26.1.1. DASD subsystem

Linux disk support for the traditional zSeries disks is provided by the DASD driver code, dasd.c. It provides support for Count-Key-Data (CKD) and Fixed Block Address (FBA) disk devices, as well as VM minidisks. The DASD driver uses channel I/O to perform read and write operations.

There are currently three ways to format disks used by Linux:

  1. dasdfmt

    The DASD driver in Linux for zSeries and S/390 comes with the dasdfmt utility to format the disks. It formats all tracks on the disk with a fixed block size. There is no support for this particular format in existing S/390 software.

  2. CMS FORMAT

    The FORMAT program in CMS also formats the disk with fixed block size, but adds a special eye catcher ...

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