Building such a storage behemoth is not the challenging part. Filling it with data, backing it up, and keeping the RAID rebuild time under load on such monster drives below the average drive failure time is the challenging part.

At that scale it makes sense to start thinking about alternatives to RAID e.g. an object storage with erasure coding should work well for a code base already using the S3 API. In theory even minio should be enough, but I never had enough spare hardware to perform a load test of that scale.