> > > Yes, there is, but you run into data integrity problems, and data > > > synchronization problems. ... > > My experience has been different. > But I understand the point and agree that there is a large exposure. > Experience from read-only volumes mounted read-write and using the > older DASD driver would seem to suggest it can get NASTY. > > ... > > > possibility would be to have multiple copies of /usr, and update the VM > > > guest's CP directories to point to the most recent one so that when the > > > system is shutdown, logged off, and back on again, it will pick up the ne > w > > > file system. > > Or use a DCSS in place of DASD. ;-) > > > > Unless you're talking about enough images being run that DASD > > > space is still conserved, it's kind of pointless. > > It's not exclusively a resource conservation thing. > It's also a system management thing. > > Say you're migrating from Wintel to L/390. > If all you do is put N PC workloads into N v-machines > you haven't reduced any of the manpower load or headache, > you've blown a good portion of what we could win with zSeries. > > Correct: three images isn't enough to bother sharing. > Correlation: three images isn't enough to justify zSeries. > > > Could someone with /usr mounted ro try this? > > Try which part? Writing to a volume that is read-only to others? > Been there; done that; and it did not cause me any pain. > I did NOT run any exhaustive test, so "it depends". ;-) > > > mount /usr -o remount,ro > > A good thing to do is mount the shared volumes read-only on the master > and then 'mount /usr -o remount,rw' when you need to update. > Hopefully you won't need to do this more than once or twice > before re-IPLing the sharing systems so that they'll be current. >
My supposition is that remounting /usr as above will cause it to resync with what's on the disk. If it works, it will save from the need to reboot after updating the master. Mind you, I would recommend doing any when the system's quiet. It's not just files that will get changed, but directories too, and if some directory gets put where your guest thinks there's a file (or vice versa) then things might get chaotic. Perhaps, on reflection, the idea's not worth much. Something to try though in a test environment where a system crash won't be painful. -- Cheers John Summerfield Microsoft's most solid OS: http://www.geocities.com/rcwoolley/ Note: mail delivered to me is deemed to be intended for me, for my disposition.
