>> You can do it to a box that hasn't been set up with mdadm... > > Sure but you will need LVM set up. I always have. > In that case, why not use LVM's snapshot capabilities? Because that doesn't do what I want. I'm not looking to have a LVM snapshot. I'm looking to have a duplicate disk. This allows me to experiment on one, whilst keeping the other safe. Alternatively, it allows me to migrate from one disk to another without too much risk - before anyone points me at pvmove, I lost a filesystem when that fell over on a live machine once :-( > You might find this works better for this particular use of mirroring > but you can also try the --splitmirrors option to the lvconvert > command (but it will be less efficient since it will take a > block-by-block copy of the origin during the lvconvert -m1 rather than > just recording changes as a snapshot would). Mirror splitting was > added in 2.02.88 (about nine months old). --splitmirrors would seem to do what I'm after *except* that it will leave the mirror unbootable without further attention (the machine won't boot with the wrong name on the LVs) > I've found that dracut doesn't always handle LVM errors particularly > gracefully (in particular if there is a problem the dracut main loop > appears to reset state after leaving the interactive shell so even if > you do fix the problem such that the system could continue to boot it > will just fail in the same way again) and by the sound of it this > could be improved for your case too. This is true - but sorta misses the point; a LV mirror is not a LV mirror if it won't activate. Adding a mirror means that a faliure of *either* side renders the whole unusable. > Ideally you'd want the initramfs scripts to carry out the same actions > as the defined mirror repair policy during startup (or to invoke > lvconvert --repair to do the same). Well, we can call it Somebody Else's Problem, or perhaps LVM should be able to use a broken mirror - that's how every other mirror system works, and is generally the very reason for having a mirror at all. I consider this to be a bug within LVM. Vic. _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
