On Tue, 15 Feb 2011 15:50:00 +0000, Stefan Hajnoczi <stefanha@xxxxxxxxx> wrote: On Tue, Feb 15, 2011 at 10:15 AM, Thomas Broda <thomas@xxxxxxxxxxxxx> wrote: Using O_DIRECT, performance went down to 11 MB/s on the hypervisor... Hmm...can you restate that as: host X MB/s guest Y MB/s Trying dd with "oflag=direct" an "of=/dev/vg0/lvtest" (directly on the KVM hypervisor) yielded a result of 11MB/s. If I try this on the guest with /dev/vda1 as output device, results are between 1.9MB/s and 7.7MB/s, usually around 3.5MB/s. To sum it up: Host: 11 MB/s Guest: 3.5 MB/s I've checked the RAID controller in the meantime. It's a HP Smart Array P400. Write Caching is switched off since the contoller has no BBU (yet). Could it be related to this? -- Thomas -- 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
