TotallyHosted has put a lot of effort into the backup sites of its customers. All our hosting servers run in RAID 1 (mirroring) or RAID 5 (striping), which means that all the data you store on the server is automatically written to multiple hard drives. Should a disk fail, then another disk will take over automatically. We can replace a hard disk (hot swap!) at a quiet time, and rebuild RAID data in the background so the websites hardly suffer from downtime.
But that is not all. We have a "NAS" (Network Attached Storage) with several terabytes of storage in both of our datacenters, especially for the backups of our clients.
All data is stored on the specific server, and then forwarded to the NAS. We always keep one complete backup of data available; in addition there are 14 incremental backups made. So we can go up to 2 weeks back in time in terms of restoring files.
Because all the data stored on multiple hard drives, your data is always safe, even if multiple hard drives fail.