There are multiple options but spanned volumes aren´t one of them because the performance is really bad.
You have the option to do the following:
1) Standard Server with good Raid Controller (MS HCL) and disks. Like Cisco s3260, HPE Apollo and all the other standard Servers.
2) A standard Storage System... Like HPE 3PAR, NetApp E-Series, Unity/SC/..., IBM StoreWize
3) A filer
4) A deduplication device like HPE StoreOnce/Exagrid/Datadomain/HPE Nimble SFA
5) other files/block based storages
Beside the dedup devices you should not use any kind of deduplication outside of Veeam.
For block volumes you can use ReFS instead of NTFS to use fast block cloning technology for merges and GFS full processing.
As it is secondary storage, I would go with the best price/capacity one from the above.