Initially when we started to use Oracle VM we did lot of performance testing and at that point we went with Paravirtualized VM’s (PVM) due to better performance we saw with them.

Now with our recent upgrade to Oracle VM 3.4.2 if you are using hugepages (we do!) then hugepages are not supported anymore with PVM guests. Oracle used to recommend running PVM virtual machines but now the recommendation is more to use Hardware virtualized (HVM) VM’s with paravirtualized (PV) drivers. If you use Oracle Enterprise Linux 7 then PVM is not an option anymore on domain selection.

Few notes which show up on MOS if you search on this topic:

Hugepages Deprecated for PVM Guests For OVM PVM Guest on OVM 3.4.X (Doc ID 2216622.1)
Cannot Enable High Availability (HA) for Virtual Machines with HugePages (Doc ID 2225673.1)

My goal was to see if there is any difference on I/O performance when you are using HVM PV guest on Oracle VM 3.4.2 compared to PVM guest. To test this I used FIO which I used also initially when we were evaluating Oracle VM performance and scripts made by Kyle Hailey. More details on these scripts here:

https://github.com/khailey/fio_scripts

The scripts run a series of tests but here I will only show the throughput and latency from sequential large reads. For the note our Oracle VM storage network is 10GbE iSCSI network using multipathing.

ovm342throughput

ovm342latency

On our use there doesn’t seem to be much difference on guest domain even though HVM PV seems to be better in these tests! I could get bit better results on PVM guests and bit worse results with HVMPV guests on further runs so they would be closer to each other in the end.

Other FIO tests followed same pattern and I ran second series of tests with Oracle’s Orion and they were as well identical so no huge difference between domains.

For us using Oracle VM 3.4.2 and switching to HVM guests with PV drivers does not seem to be an issue. If you are considering this I recommend to test it as well to see how it works in your environment. Depending on your setup you might get different results, specially if you are using iSCSI network for storage!

 

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