z/VM employs the concept of "minidisks", whereby physical DASD can be split into smaller sizes, or minidisks, and assigned to individual VM guest systems. In this tip, we describe an approach for dedicating whole DASD volumes for Linux systems. These volumes are then split into minidisks owned by individual Linux guests.
If DASD has been “genned shared” in the zSeries IOCDS, it is visible to multiple logical partitions (LPARs) on the machine.
In order to be able to distinguish Linux volumes from DASD on other zSeries operating systems, we recommend initializing and labeling all the Linux DASD with a volume serial that makes it obvious that these are Linux disks.That way, if one or more of the disks is inadvertently varied online to another LPAR on the machine, it should be obvious that the disk belongs to the Linux environment.
In our examples, we use the following volume serial naming convention: V2LXnn. V2LX identifies these volumes as Linux volumes belonging to the VM2 LPAR, while nn is the sequence number (in hexadecimal) of the volume.
To format and label a DASD volume, follow the sequence of steps outlined below. User input is denoted in bold.
attach 3101 *
DASD 3101 ATTACHED TO MAINT 3101 WITH DEVCTL
ENTER FORMAT, ALLOCATE, LABEL, OR QUIT:
ENTER THE VDEV TO BE PROCESSED OR QUIT:
ENTER THE CYLINDER RANGE TO BE FORMATTED ON DISK 3101 OR QUIT:
ENTER THE VOLUME LABEL FOR DISK 3101:
FORMAT WILL ERASE CYLINDERS 00000-00000 ON DISK 3101
DO YOU WANT TO CONTINUE? (YES | NO)
HCPCCF6209I INVOKING ICKDSF.
ICK00002I ICKDSF PROCESSING COMPLETE. MAXIMUM CONDITION CODE WAS 0
ENTER ALLOCATION DATA
ICK00001I FUNCTION COMPLETED, HIGHEST CONDITION CODE WAS 0
Begin by attaching the DASD device to the VM guest. Next, invoke the cpfmtxa utility to format the volume. The utility prompts for the device number to format (3101, in our case). Specifying a cylinder range of 0 0 will format cylinder 0. The remaining cylinders will be formatted by Linux using the dasdfmt command (for details on using the
dasdfmt command, see http://www.ibm.com/redbooks/abstracts/tips0277.html). The cpfmtxa utility prompts for a DASD label (v21x01, in this case). Finally, the cpfmtxa utility requests verification before proceeding; respond yes when requested.
Upon completion, the DASD volume is available to be partitioned and formatted by Linux guests.
This material has not been submitted to any formal IBM test and is published AS IS. It has not been the subject of rigorous review. IBM assumes no responsibility for its accuracy or completeness. The use of this information or the implementation of any of these techniques is a client responsibility and depends upon the client's ability to evaluate and integrate them into the client's operational environment. publib-b.boulder.ibm.com