> > 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 new > > 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.
