Anthony Liguori wrote: >>> >>> 2/ two instances of kvm can be passed the same -hda. There is no >>> locking whatsoever. This messes up things seriously. >>> >>> >> >> These two are upstream qemu problems. Copying qemu-devel. >> >> I guess using file locking by default would improve the situation, >> and we can add a -drive ...,exclusive=no option for people playing >> with cluster filesystems. >> > > This is not a situation where the user has a reasonable expectation of > what will happen that we violate. If the user is unhappy with the > results, it's because the user made a mistake.
Well, one user (me) has made this mistake, several times. > FWIW, the whole override thing for Xen has been an endless source of > pain. It's very difficult (if not impossible) to accurately determine > if someone else is using the disk. What's wrong with the standard file locking API? Of course it won't stop non-qemu apps from accessing it, but that's unlikely anyway. > Also, it tends to confuse people trying to do something legitimate > more often than helping someone doing something stupid. -drive exclusive=off (or share=yes) > > I very frequently run multiple VMs with the same disk. I do it > strictly for the purposes of benchmarking. There are ways to share a > disk without using a clustered filesystem. I imagine only raw format disks, and only as non-root filesystems (or with -shapshot, which should automatically set exclusive=off)? > > If a higher level management tool wants to enforce a policy (like > libvirt), then let it. We should not be enforcing policies within > QEMU though. I agree that qemu is not the place to enforce policies, but covering a hole that users are likely to step into, while allowing its explicit uncovering, is a good thing. We're not enforcing the policy, only hinting. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
