On 07/21/2010 09:27 AM, Takuya Yoshikawa wrote: > Hi, > > > We are now checking about what we should do on vm fail-over. > > Concerning this, does anybody know about any danger about data > consistency when we are using shared disk? > > > What I'm concerning is if crashed VM-side host is still holding > buffered data, starting a new VM instance on another node may > result in file system corruption. > > This problem may similar to live-migration but little bit different > in the sense that VM is crashed -> cannot do anything from that point. > If the VM can't do anything, you're safe. Of course a crash doesn't mean a VM can't do anything, you typically need to isolate it by resetting the host or having a switch disconnect its storage and network. > > How about the combination of old or new guest OS and the following > settings? > > - writethrough > - writeback > - none > > If needed, we'll do sync by HA-side scripts before starting a new VM > instance. > I believe nothing special is needed, as long as a crash means both the qemu and host kernel crashed. If only qemu crashed, then the writeback case needs buffers flushed. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
