Redundant Array of Independent Disks, or RAID, is a method of saving content on multiple hard drives at the same time. A RAID could be software or hardware depending on the drives that are used - physical or logical ones, however what is common between them is that they all operate as just one single unit where info is stored. The top advantage of employing a RAID is redundancy as the information on all drives will be exactly the same all the time, so even in the event that a drive fails for whatever reason, the info will still be present on the remaining drives. The general performance is enhanced as well because the reading and writing processes can be split between different drives, so a single one can't be overloaded. There're different types of RAIDs where the performance and fault tolerance may differ based on the particular setup - whether information is written on all of the drives real-time or it's written on one drive and afterwards mirrored on another, what number of drives are used for the RAID, etcetera.
RAID in Website Hosting
The state-of-the-art cloud web hosting platform where all website hosting accounts are generated employs fast SSD drives instead of the traditional HDDs, and they work in RAID-Z. With this setup, a number of hard drives function together and at least one is a dedicated parity disk. Put simply, when data is written on the remaining drives, it is copied on the parity one adding an extra bit. This is done for redundancy as even in case some drive fails or falls out of the RAID for whatever reason, the data can be rebuilt and verified using the parity disk and the data recorded on the other ones, thus practically nothing will be lost and there will not be any service interruptions. This is an additional level of security for your data along with the state-of-the-art ZFS file system that uses checksums to make sure that all the data on our servers is intact and is not silently corrupted.