Re: Running FreeBSD 14.3 under XCP-NG performance issues

> Am 22.07.2025 um 23:06 schrieb Tom Arnold <xyzzy@sysabend.org>:
> 
> I've been trying to get FreeBSD happy under our new XCP-NG setup.
> 
> The biggest problem I'm seeing right now is disk performance.
> 
> I built the VM on a 200gig LUN mapped from a Dell MD5.  This disk happened to
> show up as /dev/ada0 and was installed with ZFS on Root.
> 
> After rebooting I added some more LUNs and put ZFS on them. These disks happen to
> show up with /dev/xbd# as Xen seems to be being detected after the reboot.
> 
> Doing a simple performance test with dd ( if=/dev/zero of=file bs=1m ) on anything
> with a /dev/ada# entry I get a transfer rate of something around 6777 MB/s.
> 
> Doing the same test on a device that is /dev/xbd# I get around half that.
> 
> If I fight a bit and disable xenguest and get one of the "newer" LUNs over to a
> /dev/ada# device the performance goes up into the 6777 MB/s range.
> 
> I figure I'm doing something wrong here but docs seem to be sparse on this and
> Vates doesn't fully support FreeBSD so its a YMMV sorta thing.
> 
> Any suggestions?
> 


XCP-NG is Xen, right?

Many, many years ago, I had similar problems with XenServer and FreeBSD.

I opened a PR or two but nothing ever came out of it (you can find them

We switched to KVM with Openstack and the problem was more or less the same - until about FreeBSD 14.2, when I seemed to see a remarkable performance-increase - though I haven’t benchmarked it.