Re: Poor harddrive performance on VM

[Paul Leiber <paul@xxxxxxxxxxxxxxxx>]

Am 01.11.2024 um 11:17 schrieb KAĞAN IŞILDAK:
> Hello,
>
> I am using Xen 4.18. My host machine is a Dell server with dual Intel®
> Xeon® Gold 6438Y+ CPUs and an NVMe SSD. I am working with Windows
> virtual machines and experiencing issues related to hard disk speeds.
Windows DomU means that it is a HVM type of VM.

> So far, I have conducted a total of four tests, covering disk format
> and BIOS firmware. I have tried both QCOW2 and RAW disk formats and
> booted the BIOS as both SeaBIOS and OVMF. In all four tests, my
> read/write speed was around 50 MB/s, which is really low.
>
> What could be causing this issue?
>
> Note: No PV driver is installed, and I have tried mounting the disks
> as both HDA and XVDA, but the results were the same.
IIUC, the PV on HVM drivers are necessary to gain the benefits of 
paravirtualization. If there is no frontend PV driver counterpart in the 
DomU for the PV backend on the Dom0, then less efficient software 
virtualization happens. [1]
I'd try to install the PV drivers. In my Windows VMs, the Xen PV devices 
have been detected and the Citrix drivers have been installed 
automatically by Windows Update.
Paul

[1] https://wiki.xenproject.org/wiki/PV_on_HVM