Redundant Array of Independent Disks, or RAID, is a way of saving content on multiple hard disk drives simultaneously. A RAID might be software or hardware based on the HDDs which are used - physical or logical ones, however what is common between them is that they all function as a single unit where data is kept. The main advantage of employing a RAID is redundancy since the data on all drives is exactly the same all the time, so even in case one of the drives fails for some reason, the information will still be available on the other drives. The general performance is also better as the reading and writing processes can be split between various drives, so a single one will not be overloaded. There're different sorts of RAIDs where the performance and fault tolerance can vary based on the exact setup - whether info is written on all the drives in real time or it is written on a single drive and then mirrored on another, the number of drives are used for the RAID, and so on.
RAID in Web Hosting
The hard drives that we use for storage with our ground-breaking cloud web hosting platform are not the classic HDDs, but high-speed solid-state drives (SSD). They operate in RAID-Z - a special setup intended for the ZFS file system that we work with. Any content that you add to the web hosting account will be stored on multiple drives and at least one will be used as a parity disk. This is a special drive where an extra bit is added to any content copied on it. If a disk in the RAID stops functioning, it will be changed without service interruptions and the info will be recovered on the new drive by recalculating its bits thanks to the data on the parity disk plus that on the other disks. This is done to guarantee the integrity of the information and together with the real-time checksum validation that the ZFS file system runs on all drives, you'll never have to be concerned about losing any info no matter what.