Hi,
Once you've created your storage space, you can use it on another computer. So, after we upgrade the system, it should still work.
But to keep your storage space safe, it's always recommended to back up important data before making modifications to your machine.
After you upgrade to Windows, we recommend that you upgrade your existing pools. With an upgraded pool, you can optimize drive usage and remove drives from pools without affecting the pool's protection from drive failure:
https://support.microsoft.com/en-us/help/12438/windows-10-storage-spaces
It suggests us to backup the data and re-create the storage space pool on Windows 10. According to knowledge, Windows 10 storage space adds a new feature "re-balance". It wasn`t included in previous system version. Here is a link for reference:
Storage Spaces Optimize Pool (Applied to Windows 10)
https://technet.microsoft.com/en-us/windows-server-docs/storage/storage-spaces/storage-spaces-optimize-pool
Best Regards