On Wednesday, 06/11/2003 at 01:11 MST, Jim Sibley/San Jose/[EMAIL PROTECTED] wrote: > Alan, shared tapes may have a problem under VM. I know they do when running > in an LPAR (see the disclaimer on the IBM under "restrictions" at > http://www10.software.ibm.com/developerworks/opensource/linux390/index.shtml [snip]
> So I would guess that assign ... muiltiuser would have the same problems as > an LPAR. > > The latch should be set from the INSMOD to the DELMOD, but it is NOT, hence > the strong recommendations for 2.2.16, and both streams of 2.4 NOT to use > shared tapes. Perhaps the UTS drivers are better behaved? File open-to-close doesn't sound like a very useful paradigm (but I don't know how Linux applications use tape drives) and I don't know if one part of Linux can open a tape file (tape management system, just to lock the drive and to request a tape mount) and another part of Linux subsequently opening-writing/reading-closing the same tape so that the drive is not unassigned until the tape management system closes the tape file. > The CP attach multiuser sounds like it relies on the hardware > assign/unassign and you could find yourself with two EC's using the tape at > the same time under Linux. > We have verified that, in LPAR mode, the assign happening as I described. > Correct me if I am wrong if VM assign ... multipath uses a different > mechanism. When a tape is attached in MULTIUSER mode, the WITH NOASSIGN option is forced. The assign/unassigns issued by the guest are propagated to the drive and are used by CP to logically move the drive among the sharing guests. Alan Altmark Sr. Software Engineer IBM z/VM Development
