Slow disk performance on Windows OS

[netaccs]

Hello,

When Windows OS is installed (7, 10) there is slow disk performance, even using this guide.
CEPH is configured with 3 servers, every one of them has x3 (9 OSD Total) SSD 870 EVO 4TB, one pool only.

This is result of with write cache back enabled, virtio drive.

Some tests on different proxmox virtual environment where made and results was same. With No enabled write cache back, results are worse.


This is result of desktop pc (non virtualized) with single ssd drive (those types of ssd (Intel and Samsung) have similar 1:1 performance on standalone computer.


In the same time Unix/Linux based virtuals have great performance - disk speed, iops and etc.

Have you got any idea why Windows's work like this way?
Does anyone have same issues?

Thanks in advance !

 

[FrenzyBR]

I'm facing the same problem, my Windows guests get cut in half of SSDs (Sata and NVME) speeds IOPs, latency... VirtIO Drivers installed during the OS installation, tried every type of controller and cache, the fastests until now VirtIO Block with write_back, and SCSI Single.

Even with NVME and Sata SSD's the latency always around on 250 μs on Windows VMs, while on Ubuntu VMs the NVME 80-90 μs and Sata 140 μs

 

[_gabriel]

CEPH (and ZFS) require datacenter ssd because they have PLP which allow fast and secure write.

btw, Windows write cache in its device manager need to be turned off to compare to an hypervisor.

 

[FrenzyBR]

Just an update, fresh new installation, using virtio drivers on boot install, SCSI Single, io_threads and write_back, of wServer 2k22 on LUN-passthrough SSD, scsi0 from HBA, perfomance better than baremetal windows installation on the same SSD.


Latencies range from 120 to 200. - Real World Performance profile

P.S. I didn't understand why the read/write speed exceeded the physical capacity of my SATA SSD (510mbs). he is not inside my zfs pools

 

[_gabriel]

because pve side writecache is another cache in addition of the guest os writecache which is another cache in addition of disk cache itself.
if guest os or host crash or power lost, data lost can prevent boot guest os or corrupt app data within guest.
it's unsecure for production server.
I'm disabling Windows writecache itself, when using datacenter ssd, there isn't performance penalty.