Both results show a really high bandwidth but I can't get that speed for file transfers.
Well, at least we can more or less exonerate networking :) Though frankly I've always felt that virtio was better than an emulated NIC.
How much memory to you have in the VM receiving the 4 GB file being transferred? One hypothesis, and it is only a hypothesis, is that the reason the file transfer goes quicker at the beginning (if I recall correctly) is the receiving VM is still just writing to filecache within the VM itself. Once the number of ditry pages in the filecache gets to some limit (which I can never remember) a flushing daemon will kick-in and start pushing pages out to "disc" (well, what the VM thinks of as its disc, whatever you've setup there). At that point there may still be something of a "race" between the arriving bytes of the file and the flushing and if there ends-up being enough memory consumed by the filecache, writes to the file will end-up getting blocked, waiting for space to free-up. And that won't happen any faster than the flusher can get them out.
And then there can be the similar thing happening between the VM and the host, where in this part we can think of the VM as being akin to the scp receiving process.
happy benchmarking, rick jones _______________________________________________ Mailing list: http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack Post to : [email protected] Unsubscribe : http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack
