ISSUE: Windows Server - Cache - Write Speed

[a.giordano]

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:


Server:



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



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

Desktop PC:



Server:



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?

 

[a.giordano]

up please

 

[Alvaro]

Hi, I have the exact same problem. I created a VM with Windows Server 2022 without installing domain control and the write cache of the C: disk is active then, added Domain Control Active Directory role and restarted the VM, the write cache of the C: disk is not active. I changed the Host server but the problem remains. Who can help me?

 

[Alvaro]

Solved: to make disk write cache active permanently, you need to edit the windows registry file and add a string in: HKLM\System\CurrentControlSet\Services\NTDS\Parameters Value: "DSA Heuristics" Type: REG_SZ Setting this to "1"
(Note: the type MUST be a string type) prevents AD service from disabling write
cache.

 

[_gabriel]

Domain Control Active Directory role and restarted the VM, the write cache of the C: disk is not active

it's the default behavior of Windows Server.
Disable OS write cache prevent AD database loosing data if crash or power failure.