On Wed, Mar 13, 2013 at 4:04 PM, Mark Post <[email protected]> wrote: ... > I think the best method is to CPFMTXA at _least_ cylinder 0 > before giving it to a guest. It really should be the entire volume, > or use the DIRMAINT function to erase things for you.
I mostly agree with Mark: clip the disk, so to speak. Linux wants 4K blocks when using ECKD. (CMS does too.) We go to a lot of trouble to pre-write these blocks, and we call it "formatting". (In the PC world, this was called "low level formatting" back in the days when they still bothered.) If we then also choose to use CDL, we have to put a special record structure in the first track so MVS will be happy. For all other ECKD formats used by Linux, the entire disk is blocked uniformly. If you're going to make it a CDL volume, then 'dasdfmt' must create the funky MVS-compatible VTOC, and the driver needs to allow that w/o a lot of grief and magic. CPFMTXA of the first cylinder usually clears the road for that action. (Or a CMS FORMAT of the first cylinder. Either should suffice.) [topic drift ... forgive me, but the simplification may prove constructive] Other architectures got away from tracks-and-records quite some time ago. Some might think it's nice that in the mainframe world we still have that option. But the pain (here for example!) just does not seem to be worth it. If your storage vendor can present FBA on the channel, try it. (Some DASD subsystems *can* do this.) Or if you have SAN, there are several ways to use it with Linux. THE ONLY time Linux actually *needs* CDL is when the disk will be shared with MVS. -- -- R; <>< ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] 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/
