ISSUE: Windows Server - Cache - Write Speed

a.giordano

New Member
Apr 19, 2024
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I’ve recently started using Proxmox and I’m testing the technology before deploying new machines. During my tests, I’ve encountered disk write speed issues. I performed tests on both a desktop PC and an HPE server.

Desktop PC Configuration:
  • CPU: Intel Core i7-7700
  • RAM: 16GB DDR4
  • Storage: ZFS RAIDZ array with 3 SSDs (240GB each)
Server Configuration:
  • Server Model: HPE ML350 GEN10
  • RAID Controller: SA P408i-a with 2GB cache and with backup battery
  • Storage: RAID10 array of 4 SSDs, configured in Proxmox as LVM
In both configurations, I created two Windows Server 2022 VMs with virtual drives configured as VirtIO SCSI.
The read speed is excellent in both cases, especially on the server utilizing the integrated controller.

However, the issue lies with write speed.
By default, the speed tests yield the following results:

Desktop PC:
Screenshot 2024-05-10 085942.png

Server:
1715353455273.png


Upon checking the disk settings, I noticed that a specific checkbox is disabled after each reboot.

Screenshot 2024-05-10 085812.png

Enabling the cache in Windows improves write speed to the correct parameters.

Desktop PC:
Screenshot 2024-05-10 090151.png


Server
:

1715353085901.png

At each Windows restart, the cache is only disabled on the operating system disk, while on the additional disks, the write cache option remains active. This is indeed a very strange behavior. Do you think there might be something wrong with the Proxmox configuration? Or could there be another reason?

In VMware, I have never encountered these issues.
I have never worried about enabling write cache on Windows. The ML350 host was configured with 3 SAS disks in RAID5 and achieved read and write speeds of approximately 6000MB/s.

Could you assist me with this issue?
 

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