Matthias Petermann <m...@petermann-it.de> writes: > Constellation 1 (Pure NetBSD kernel): > > * NetBSD/amd64 9.0 Kernel + Samba: throughput ~60 MByte/s > > Constellation 2 (NetBSD/Xen Domain 0): > > * Xen 4.11 + NetBSD/Xen Dom0 + Samba: throughput ~12 MByte/s > > I measured this by copying an 8 GB ISO file from a Windows host. > In constellation 2, no guests had started and the full main memory of > Dom0 was assigned. In my view, the only significant difference is that > NetBSD can only use one of the two CPU cores under Xen. Since the CPU > was idle on average at 20% during copying, that doesn't seem to be the > bottleneck? > > Are such differences in I/O performance to be expected?
Other than the 1 cpu vs ? cpus, no. I tested xen perfmorance long ago, in 2006 with a setup NetBSD dom0 disk file in filesystem NetBSD domU with xbd0 from the file and found that reading with dd: the dom0 raw disk was just about the same as bare metal the file was maybe 5-10% slower (maybe not quite; it was noticeable but not a big deal) the xbd0d "raw disk" was also 5-10 % slower than reading the file in the dom0 Now, this isn't what you asked, but I find the difference you found seem like a bug. I would definitely do dd from the raw disk in your case 1 and 2, followed by dd of the iso. Also, I would repeat your tests and run "systat vmstat" during each case, and also netstat to see if the network interface is not keeping up. Then I would run iperf, ttcp or whatever to test network separate from samba and disk.
