Edited by: rukbat on May 18, 2012 11:22 AM
@ user 881340,
Manually creation and testing of a dmnfs device on the OVM node reproduces the same poor performance results, creation of a nfs loop mounted image produces normal results..
On OVM 3.1.1 dmnfs is used to mount the .img files stored on a NFS SR. I dont know for sure but I suspect that a HVM guest does not use dmnfs, but thats just my speculation on why pure HVM performs normally.
After upgrade from 3.0.3 to 3.1.1, we are seeing a huge performance descrease on the VM server when performing a file copy on a iscsi target (e.g. on /dev/mapper/36090a09800c7ccdd21f71404000020a5 mounted on /OVS/Repositories/0004fb0000030000f26284ca7d00398d) - this obviously also affects all virtual machines. We have an Intel X520-DA2 adapter (10Gbe) and an Equalogic PS6010XVS iSCSI box.
I guess this is different from your problem if you only have issues with virtual disks.