Redundant Array of Independent Disks, or RAID, is a way of keeping content on multiple hard disks concurrently. A RAID could be software or hardware depending on the hard drives which are used - physical or logical ones, however what’s common between them is the fact that they all work as one single unit where your information is saved. The key advantage of using a RAID is redundancy since the data on all the drives is the same all the time, so even in the event that some drive fails for some reason, the information will still be present on the rest of the drives. The general performance is also better since 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 functionality and fault tolerance may vary depending on the specific setup - whether info is written on all of the drives in real time or it is written on one drive and then mirrored on another, what number of drives are used for the RAID, etcetera.
RAID in Shared Hosting
The state-of-the-art cloud Internet hosting platform where all shared hosting accounts are generated employs quick SSD drives as opposed to the traditional HDDs, and they work in RAID-Z. With this configuration, multiple hard drives operate together and at least a single one is a dedicated parity disk. Basically, when data is written on the rest of the drives, it's 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 some reason, the info can be rebuilt and verified using the parity disk and the data recorded on the other ones, thus absolutely nothing will be lost and there will be no service disorders. This is one more level of protection for your information together with the top-notch ZFS file system which uses checksums to ensure that all the data on our servers is intact and is not silently corrupted.