If you want to keep your data on-site, unless your already have a lot of the infrastructure that you can leverage the path of least resistance is to use something like a NetApp Filer.
For backups it can create snapshots on a schedule (hourly/daily/weekly), then either replicate them to a second physical storage unit (hopefully at a different site) or present them to your backup solution.
Using the file services on the NetApp will also provide a solution to your "how do I present it to the storage consumers" question - iSCSI, CIFS with domain integration, NFS, Fibre Channel... You also get storage level de-duplication and compression, if that works for your data.
Of course you will pay what seems like a lot for it, but it does solve a lot of your problems in one unit. How much will it save in servers, backup capacity, a multi-drive tape library, daily visits to the server room to reload tapes and so on.
But if your data center isn't up to providing the level of availability you want then any hardware solution is going to be problematic - large storage systems do not like having the power pulled out from under them. Minimum is dual-redundant UPS power and fault tolerant cooling, or you will most likely have problems.