On 9/26/11, Robin Lee Powell <rlpowell@xxxxxxxxxxxxxxxxxx> wrote: > On Mon, Sep 26, 2011 at 01:49:18PM +0800, Emmanuel Noobadmin wrote: >> On 9/25/11, Robin Lee Powell <rlpowell@xxxxxxxxxxxxxxxxxx> wrote: >> > >> > OK, so I've got a Linux host, and a bunch of Linux VMs. >> > >> > This means that the host *and* all tho VMs do their own disk >> > caches/buffers and do their own swap as well. >> >> If I'm not wrong, that's why the recommended and current default >> in libvirtd is to create storage devices with no caching to remove >> one layer of duplication. > > How do you do that? I have my VMs using LVs created on the host as > their disks, but I'm open to other methods if there are significant > advantages. It's unrelated to what you're actually using as the disks, whether file or block devices like LVs. I think it just makes KVM tell the host not to cache I/O done on the storage device. To do so just use the option cache=none when specify the storage. e.g. from http://www.linux-kvm.org/page/Tuning_KVM qemu -drive file=/dev/mapper/ImagesVolumeGroup-Guest1,cache=none,if=virtio or edit the cache attribute in the libvirt domain XML file if you're using that. -- 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
