[SOLVED] Slow NVMe SSD performance in guest ubuntu (400 MB/s instead of 2000 MB/s)

[Sandbo]

I have a guest ubuntu 20.04.2 where I tried to pass two Kingston A2000 1TB to, this is done by passing them as PCI Device, with PCI-E flag checked.
The advertized speed is up to 2000 MB/s write.
With the drives empty, I found while read speed is 2000 MB/s as expected, the write speed is limited to ~ 400 MB/s.

Is there something I missed?

The system is running on AMD 1950X with Proxmox 6.3.6.

Update: Turns out to be an ubuntu issue apparently, in the same host, a Windows guest could give 1.7 GB/s write. Strange.

Update 2: Using KDiskMark I got the same result as AS-SSD on Windows, problem resolved!

 

[ermanishchawla]

I have a guest ubuntu 20.04.2 where I tried to pass two Kingston A2000 1TB to, this is done by passing them as PCI Device, with PCI-E flag checked.
The advertized speed is up to 2000 MB/s write.
With the drives empty, I found while read speed is 2000 MB/s as expected, the write speed is limited to ~ 400 MB/s.

Is there something I missed?

The system is running on AMD 1950X with Proxmox 6.3.6.

Update: Turns out to be an ubuntu issue apparently, in the same host, a Windows guest could give 1.7 GB/s write. Strange.

How did you check the write ?? if you have disk cache enabled, the disk performance would be different, additional OS also have cache parameters

Try with fio

 

[Sandbo]

How did you check the write ?? if you have disk cache enabled, the disk performance would be different, additional OS also have cache parameters

Try with fio

Thanks for the suggestion, indeed GNOME-DiskUtility which I used was the problem.
Using KDiskMark I got the same result as AS-SSD on Windows, problem resolved!