I have a Citrix XenServer 6.1 installed on a HP Server (1x Intel Xeon E5630 @ 2.53GHz (4 cores, 8 threads, RAM: 752MB for dom0 and 55286MB for the guests). The server has 2 scsi mirrored disks and is used for dev/testing.
The host runs 5 guests that I powered on or off during the tests. Most of the perf tests gave poor results. But I'd like to tune Xen: for instance, a "dd if=/dev/zero ..." gives 130MB/s on the host, but only 75MB/s on a lone guest.
If I run a
dd if=/dev/urandom on a guest, the CPU is saturated and I get 7MB/s.
tune-vcpus, I managed to give 8 vCPUs to dom0 and I got less perfs. The default is 4 vCPUs and I'd like to give dom0 only 1 vCPU but it doesn't work.
Here is what I tried:
/etc/sysconfig/tunes-vcpus> NR_DOMAIN0_VCPUS=1 and MAX_NR_DOMAIN0_VCPUS=1
- reboot the host
I also tried
/opt/xensource/libexec/xen-cmdline -set-dom0 blkbk.reqs=256
to get more perf from the storage it doesn't change anything.
And I enabled Qos on the VBDs and gave the highest priority to the one where I do my tests.
After all that, I don't get any gain in I/O performance. Is there anything else to do?