Here is a little more info about VOL1 capabilities. The official IBM standard only requires 80 bytes, far less than the 512 bytes reserved for MBR. The MBR reservation is common for many filesystems (EXT2/3/4 and others). You can have a VOL1 label while keeping the FS at the front of the disk. It fits. Things continue to work.
This is really useful for systems like zPDT because you can 'mount -o loop' the file defining the disk on the host system. Similarly, a PV could be "attached" to Linux on zPDT, happily with VOL1 label. (Same for an LV, of course.) "But wait, there's more!" A physical disk could be attached to Linux on zPDT. (Though not partitioned if stamped VOL1.) Alan said, "Linux could obtain, via IBM channels, an official VOL1 standard version ID." IPL text for FBA DASD also fits in "MBR space". So why CDL? Because it provides a VTOC and flattens the learning curve for MVS shops. (Hence the comment "MVS needs to grow up.") Then what's wrong with CDL? It truncates records at the front of the disk rendering all other uses void. (filesystems, partitioning, PV) The VOL1 standard does not require this; it doesn't mandate end-of-record at 80 bytes. Think about interoperability. VM shops might prefer a CMS reserved file where MVS wants a DS. (The label would be "CMS1". Holy minidisks, Bat Man!) Going extreme ... ISO-9660 (CD-ROM) reserves a whopping 32K. I recall putting a traditional PC partition table at the front of a minidisk with a boot partition following the ISO-9660 FS. -- R; <>< ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
