Proxmox 5.4-6 VMs very slow


New Member
Feb 15, 2018

I have a slow problem with my VMs (linux / windows) under proxmox, despite the server is efficient server (12 CPU, 64 GB RAM),
I gave the machines a lot RAM and CPU but still the slowness exists, as well as the internet connection is perfect

Thank you,

Make sure you use the following configs for your VMs:
  1. VirtIO network adapter
  2. VirtIO SCSI as SCSI controller
  3. SCSI disk type (also VirtIO drivers)
Keep in mind that often the bottleneck can come from the drives (RW speed, IOPS), so make sure you use efficient storage setup (e.g. ZFS RAID10 on a minimum 4 drives, preferably enterprise SSDs, given that you can make sure the drives are passed directly to OS).

Hope it helps!
And i just realised that "slow" can have a different meaning for different people. If you're saying that, e.g. Windows GUI is lagging, keep in mind that GPU resources are not virtualised, so basically your VM machines have no GPU to rely on. This means that all the graphical operations can perform poorer than, say, on a laptop.
I have a slowness even if at the level of the execution of the tasks

How do you measure that? A good thing do initially do would be to do a benchmark on the host where the VMs run to get a baseline (can't really run faster in a VM then the host itself) and then do the same in the VM and compare. E.g., stress-ng for CPU/Memory, fio for storage, ifperf for network... if you search a bit you find nice tutorials/how to's about those test/benchmark programs, if you are not familiar with them. And yes, I agree with adamb, my bet is also on the storage.
How slow do you mean exactly? If you mean "catastrophically slow", did you maybe set "KVM hardware virtualisation" to "No" for the VMs? This will cause their CPU to be emulated in software, which is a complete non-starter for performance.


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