Big VMWare disk import experience/recommendation

Big VMWare disk import experience/recommendation

[Eneko Lacunza]

Hello all,

We are planning a migration of about 65 VMs from a VMWare v8 cluster to 
PVE. There is a mixture of Debian, Ubuntu and Windows machines there.

We have done that before, but during the last migration a month ago 
(unrelated customer) we had performance issues importing/converting the 
disks (WUI wizard). Some of the issues we could fix removing VM 
snapshots from VMWare, but others (with the biggest disks, about 3,5T) 
prevailed, even after checking for snapshots (no snapshots present) and 
trying to flatten the disk image. Those were file servers and we had to 
fail back to copying disk contents with robocopy, and fippling VMs to 
minimize downtime; a procedure that has its issues....

In the new migration, we have a pair of VMs with 12TB disks, and one 
with 35TB. We're afraid to suffer again the disk copy/convert 
performance issues.

Any recommendation would be much appreciated.

Regards

Eneko Lacunza
Zuzendari teknikoa | Director técnico
Binovo IT Human Project

Tel. +34 943 569 206 | https://www.binovo.es
Astigarragako Bidea, 2 - 2º izda. Oficina 10-11, 20180 Oiartzun

https://www.youtube.com/user/CANALBINOVO
https://www.linkedin.com/company/37269706/

RE: Big VMWare disk import experience/recommendation

[Kyle Sexson]

Have you looked into he 'Minimal Downtime' move option? https://pve.proxmox.com/wiki/Migrate_to_Proxmox_VE#Attach_Disk_&_Move_Disk_(minimal_downtime)

The short description is you have VMWare move the vmdk files to shared storage with PVE and then import the disks from the shared storage.  This can avoid the speed limitations with the VMWare API used by the automated process

-----Original Message-----
From: Eneko Lacunza <elacunza@binovo.es> 
Sent: Wednesday, March 4, 2026 9:58 AM
To: pve-user@lists.proxmox.com
Subject: Big VMWare disk import experience/recommendation

CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.


Hello all,

We are planning a migration of about 65 VMs from a VMWare v8 cluster to PVE. There is a mixture of Debian, Ubuntu and Windows machines there.

We have done that before, but during the last migration a month ago (unrelated customer) we had performance issues importing/converting the disks (WUI wizard). Some of the issues we could fix removing VM snapshots from VMWare, but others (with the biggest disks, about 3,5T) prevailed, even after checking for snapshots (no snapshots present) and trying to flatten the disk image. Those were file servers and we had to fail back to copying disk contents with robocopy, and fippling VMs to minimize downtime; a procedure that has its issues....

In the new migration, we have a pair of VMs with 12TB disks, and one with 35TB. We're afraid to suffer again the disk copy/convert performance issues.

Any recommendation would be much appreciated.

Regards

Eneko Lacunza
Zuzendari teknikoa | Director técnico
Binovo IT Human Project

Tel. +34 943 569 206 | https://linkprotect.cudasvc.com/url?a=https%3a%2f%2fwww.binovo.es&c=E,1,iKIS-qIMU5XaqfA8IIHrkueNLILrXA13jFJNFanqLdRXwGDcg_N1TbhjC8aBjleG6skI4b4qFKxkTdsIobmFu31yftkfHMBvTGFmtYZEJekURXNZ9WH-RpnQlVo,&typo=1
Astigarragako Bidea, 2 - 2º izda. Oficina 10-11, 20180 Oiartzun

https://www.youtube.com/user/CANALBINOVO
https://www.linkedin.com/company/37269706/

Re: Big VMWare disk import experience/recommendation

[Eneko Lacunza]

Hi Kyle,

Thanks for the suggestion. Seems that section is expanded since I last 
checked it.

We may be able to work out something so that PVE nodes export a NFS 
share to ESXi nodes, so that big disks can be migrated there and then 
converted in the background.

We'll check first with a smaller VM.

I will report back if we finally start this project, thank you!

Regards

El 4/3/26 a las 17:18, Kyle Sexson escribió:
> Have you looked into he 'Minimal Downtime' move option? https://pve.proxmox.com/wiki/Migrate_to_Proxmox_VE#Attach_Disk_&_Move_Disk_(minimal_downtime)
>
> The short description is you have VMWare move the vmdk files to shared storage with PVE and then import the disks from the shared storage.  This can avoid the speed limitations with the VMWare API used by the automated process
>
> -----Original Message-----
> From: Eneko Lacunza <elacunza@binovo.es>
> Sent: Wednesday, March 4, 2026 9:58 AM
> To: pve-user@lists.proxmox.com
> Subject: Big VMWare disk import experience/recommendation
>
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
>
>
> Hello all,
>
> We are planning a migration of about 65 VMs from a VMWare v8 cluster to PVE. There is a mixture of Debian, Ubuntu and Windows machines there.
>
> We have done that before, but during the last migration a month ago (unrelated customer) we had performance issues importing/converting the disks (WUI wizard). Some of the issues we could fix removing VM snapshots from VMWare, but others (with the biggest disks, about 3,5T) prevailed, even after checking for snapshots (no snapshots present) and trying to flatten the disk image. Those were file servers and we had to fail back to copying disk contents with robocopy, and fippling VMs to minimize downtime; a procedure that has its issues....
>
> In the new migration, we have a pair of VMs with 12TB disks, and one with 35TB. We're afraid to suffer again the disk copy/convert performance issues.
>
> Any recommendation would be much appreciated.
>
> Regards
>
> Eneko Lacunza
> Zuzendari teknikoa | Director técnico
> Binovo IT Human Project
>
> Tel. +34 943 569 206 | https://linkprotect.cudasvc.com/url?a=https%3a%2f%2fwww.binovo.es&c=E,1,iKIS-qIMU5XaqfA8IIHrkueNLILrXA13jFJNFanqLdRXwGDcg_N1TbhjC8aBjleG6skI4b4qFKxkTdsIobmFu31yftkfHMBvTGFmtYZEJekURXNZ9WH-RpnQlVo,&typo=1
> Astigarragako Bidea, 2 - 2º izda. Oficina 10-11, 20180 Oiartzun
>
> https://www.youtube.com/user/CANALBINOVO
> https://www.linkedin.com/company/37269706/
>
>
>

Eneko Lacunza
Zuzendari teknikoa | Director técnico
Binovo IT Human Project

Tel. +34 943 569 206 | https://www.binovo.es
Astigarragako Bidea, 2 - 2º izda. Oficina 10-11, 20180 Oiartzun

https://www.youtube.com/user/CANALBINOVO
https://www.linkedin.com/company/37269706/