RE: Migrating a 10TB VM from ESXi to PVE/Ceph

[Andrei Boros <andrei@srr.ro>]

I was thinking of the same thing for a esx->pve migration scenario we have.

Still in the concept stage until hardware is fully connected, so will be back with feedback.

On 7 September 2026 22:35:22 EEST, Adam Thompson <athompso@athompso.net> wrote:
>I went with NFS precisely because FC storage isn't generally something
>PVE can mount - it's block storage, so it'll have (most likely) a VMFS5
>filesystem and raw files with extents inside it, not VMDKs.  Pivoting
>through an NFS server flattens everything into a VMDK, which PVE can
>then mount and see and use.
>-Adam
>
>-----Original Message-----
>From: Tom Weber <pve@junkyard.4t2.com> 
>Sent: Monday, September 7, 2026 12:46 PM
>To: pve-user@lists.proxmox.com
>Subject: Re: Migrating a 10TB VM from ESXi to PVE/Ceph
>
>Hi,
>
>I'd try to make your FC SAN Storage visible to your PVE Cluster - so
>that it can "see" the .vmdk Files.
>
>Next define a VM with the needed Hardware Settings (CPU, RAM,
>Network...) but small / empty Disks on your FC SAN Storage - choose
>VMDK Format.
>
>This should give you a machine description in PVE (in
>/etc/pve/nodes/<NODE>/qemu-server/<ID>.conf) and vm-<ID>-disk-<x>.vmdk
>files on the FC SAN Storage.
>
>Now with the VM shut down (in both worlds), you could rename the
>production VMDK Files to the vm-<ID>-disk-<x>.vmdk names used in the
><ID>.conf file and you should be able to fire up the VM on the PVE
>cluster working with the vmware disks on the FC SAN (current Data).
>
>Once the VM is running you could do a live migration (move Storage) of
>the VMDK disk to Ceph or whatever other PVE Storage.
>
>
>From time to time I did something similar and I dont see why it
>shouldn't work but please test and experiment with smaller VMs first -
>and if possible work with Snaphots/Backups whatever before mounting the
>production .vmdk files in PVE.
>
>Regards,
>   Tom
>
>
>Am 07.09.26 um 09:08 schrieb Fabien Sirjean:
>> Dear all,
>> 
>> After successfully migrating most of our infrastructure (300+ VMs)
>from VMware ESXi to PVE, we're struggling with one last critical VM:
>our BlueMind/Cyrus mail server (~800 users), with a 10TB virtual disk.
>> 
>> Our setup is:
>> 
>> Source: ESXi → Dell EMC VPLEX (FC) → Dell Unity
>> Target: Proxmox VE → Ceph RBD (dedicated cluster)
>> 
>> We tried the Proxmox ESXi importer, but I/O performance degraded so
>much during the live import that the mail service could not sustain its
>normal workload.
>> We then stopped the service to complete the migration, but the import
>eventually failed after almost 3 days, forcing us to start over.
>> 
>> Application-level migration/synchronization is not an option, so
>we're looking for a block/storage-level approach with minimal downtime.
>> 
>> Since the datastore ultimately resides on our FC SAN, could we bypass
>ESXi entirely and temporarily present the relevant VPLEX/Unity LUN to a
>PVE or migration host, mount/access the VMFS datastore read-only, and
>copy/convert the VMDK directly to Ceph RBD?
>> Even better, is there a practical way to perform the bulk copy while
>the VM is running, then only synchronize the changed blocks during the
>final cutover?
>> 
>> Any advice or experience with direct VMFS access, VPLEX/Unity
>snapshots/clones, or other approaches for this kind of migration would
>be greatly appreciated.
>> 
>> Thanks!

-- 
ing. Andrei Boros
Serviciul IT&C
0745-115721