On 11-12-15 10:47 AM, Stefan Pietsch wrote: > > Did you try to set the cache of the virtio disk to "none"? I didn't. It was set at "default" in virt-manager and I suppose I just assumed that "default" would be reasonable. Changing to "none" has had a good effect indeed: host $ ssh guest dd of=/dev/vdb if=/dev/zero bs=1M oflag=direct count=10000 10000+0 records in 10000+0 records out 10485760000 bytes (10 GB) copied, 49.9241 s, 210 MB/s host $ ssh guest dd of=/dev/vdb if=/dev/zero bs=1M oflag=direct count=10000 10000+0 records in 10000+0 records out 10485760000 bytes (10 GB) copied, 54.7737 s, 191 MB/s host $ ssh guest dd of=/dev/vdb if=/dev/zero bs=1M oflag=direct count=10000 10000+0 records in 10000+0 records out 10485760000 bytes (10 GB) copied, 50.9851 s, 206 MB/s host $ sudo dd of=/dev/datavol/disk1 if=/dev/zero bs=1M oflag=direct count=10000 10000+0 records in 10000+0 records out 10485760000 bytes (10 GB) copied, 31.0545 s, 338 MB/s So, about 2/3 of host speed now -- which is much better. Is 2/3 about normal or should I be looking for more? Thanks much! b.
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