On Sun, Apr 15, 2012 at 5:16 AM, Ron Edison <ron@xxxxxxxxx> wrote: > The server is a Dell R710 with an H700 controller with 1gb of nvcache. Writeback cache is enabled on the controller. There is a mix of linux and windows guests, some with qcow2 format vdisks and others with raw format vdisks. Some of these guests have wb cache enabled on the vdisks and some do not. -drive cache=writeback is safe when the guest flushes appropriately. If the guest is not sending flushes (e.g. ext3/4 barrier=0) then there are no guarantees. > About a third of the guests experienced disk corruption after coming back up after the host lost power. Based on what I have read, this should not have happened using the above configuration. The operating system is Centos 6.2, this is all direct attached storage configured as raid 1 mirrors. Is the H700 battery charged? My understanding is that writethrough caching on the H700 will only be safe when the battery is present and charged. What do you mean by "guests experienced disk corruption"? I would expect the guests do an fsck when they are started again, just like a physical machine that underwent power failure. What exactly is corrupted? Does QEMU refuse to open the .qcow2 file? Is there data missing inside the guest? Has application data (e.g. database) gone into a bad state so you get errors? Stefan -- 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
