VeeaMover - NTFS DeDup to ReFS

[Lewpy]

I am planning an Veeam Repository refresh for a client, and I am wondering about the possibility of migrating datastore file system during the process.
The current Veeam repository is

• Windows Server 2019
• DAS (2 x 36TB)
• NTFS format (large block sizes)
• Windows DeDuplication

Veeam Backup Copy Jobs replicate the main backup data to this repository, for offsite backups and longer term retention using GFS retention settings in the Backup Copy Jobs.
Veeam is configured to store the data as "Dedupe-friendly".
The volume utilisations are

• Volume 1 : 164TB Veeam Backups using 14.5TB of disk space (2 per-vm backup job chains)
• Volume 2 : 152TB of Veeam Backups using 15.9TB of disk space (2 per-vm backup job chains)

So they are getting about a 10:1 deduplication saving, which is pretty good (upgrading from Windows Server 2016 to 2019 made a huge difference with the improved deduplication engine).
This server is very old, and the choice of using Windows DeDuplication was due to their being no other option. ReFS was not a usable option at the time, and there hasn't been a way to move the vast amount of data off to a similarly sized server.
Until now and VeeaMover
So my question is: could VeeaMover migrate this data to a new server, changing from NTFS to ReFS and take advantage of block cloning between all the GFS recovery points? Without this, the disk space requirements would be ridiculously high.
Is there any tool to provide an estimate of the ReFS disk space required? A "WhatIf"? There are many factors going on: ReFS block cloning, Veeam compression changing from dedupe-friendly to something more aggressive, etc.

Even using VeeaMover to move to a new Windows Server with NTFS/DeDup isn't a viable option, due to the background nature of Windows DeDuplication: you would need to copy across the entire backup chain and that would need the full amount of disk space available until Windows DeDuplication runs.

The only other option is to start afresh on the new server and store the old server until the retention points have expired.

[Immutability is handled by Cloud storage SOBR, so not really looking at a hardened repository at this stage]

Thanks

[HannesK]

Hello,
yes, VeeaMover moves "any to any".

I'm not aware of any tool that can estimate the disk space difference. My guess would be plus 10-20% (let me know how good my guess was )

Best regards,
Hannes