Time drift using q35


Active Member
Feb 4, 2016

We've been installing machines for years on proxmox without any issues, but the other day I figured I'd try q35 since it's available, just by curiosity, and I installed a few virtual machines on a single node using it.

They seem to be working fine, but the time is drifting pretty fast and openntpd is struggling to keep up :

May 23 09:25:06 vs2 ntpd[31252]: adjusting local clock by 2.647355s
May 23 09:25:38 vs2 ntpd[31252]: adjusting local clock by 2.692527s
May 23 09:27:16 vs2 ntpd[31252]: adjusting local clock by 2.761033s
May 23 09:27:46 vs2 ntpd[31252]: adjusting local clock by 2.884207s

I've never seen that before in a VM, and the only difference I can think of is that those VMs are using q35. Anyone experienced that ?
The clock source is kvm-clock as usual, and the qemu-guest-agent is installed if that matters.

in a VM you have always the problem of time drifts.
This is the reason why every Hypervisor vendor recommends to use an external timer like a NTP server
Of course, but you're talking about a few seconds a day at most, and that is the behavior with the default chipset indeed.
But using q35 we're talking about multiple minutes per hour, that's a drift of something like half an hour per day, that can't be normal.

And that's under no load, of course, just empty virtual machines.
Do you have bost and power saving in the bios active?
Because this could also a reason for this.
I don't actually know how to get into the BIOS of a VM ? Does that even make sense ?
I meant the host bios.
It is true that q35 has the other time implementation as i440fx but the source of the problem is the same.
It's OVH, I don't have access to the host BIOS.
But i440fx works perfectly fine, that problem only occurs with q35


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