Archive server disk setup and backup strategy suggestions?

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At this point we have 1.5Tb of data inside PDM.
We robocopied them for years on another storage, but it is not a good solution and we are looking at a tape device to have also an offline copy in a safer location.

Thanks to the previous admin that botched our workflows we cannot use cold storage as our supposedly released data are not labeled as such and got caught together with less useful versions.

The new bare metal server is coming next month: win server 2022 on a DL360 gen10 hp, an old hp model out of production at the end of 2024, but it is literally less then half the price of a gen11 with similar specs.

the idea is to arrange 1.9TB x 8 SSD

5 disks in raid6 250GB in c: and the rest d: drive with a perspective to use it at 60 to 70% of capability for the next 5 years.

3 disks e: drive for a local buffer to backup all the vault data before transferring them to the tape and another server.
A raid5 or raid0 + spare if possible.

the idea is to make a full vault copy during the weekend copy on the e: drive locally then copy it on the tape.

From monday to friday I would like to take a differential backup only and keep them on e: with the full backup and additionally copy them on separate tapes as well.

After one week we overwrite the full backup and start over.

How can I take an incremental backup of the PDM vault?
do you think it is worth?

Our IT idea was to have a local full backup, monday to friday folders with differential or incremental data.
rotate 8 tapes (2 full and 6 daily diff)

I am under the impression this is more a DB oriented strategy rather then one closer to a fIle system like pdm vault situation.

Any suggestion?
Software, OS or hardware setup wise.

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As a separate question to RAID experts: do you think it would be better to have all 8 disks in RAID6 and partition them as c: d: e: or setup only the core 5 disks under the RAID6 and leave the 3 disks used as a internal backup on a separate RAID?