Redundant Array of Independent Disks, or RAID, is a way of storing content on several hard drives concurrently. A RAID could be software or hardware depending on the HDDs which are used - physical or logical ones, but what’s common between them is that they all operate as just one single unit where info is stored. The main advantage of using a RAID is redundancy since the information on all of the drives is identical all of the time, so even in case some drive fails for whatever reason, the info will still be present on the other drives. The general performance is enhanced as well since the reading and writing processes can be split between a number of drives, so a single one won't be overloaded. There're different types of RAIDs where the capabilities and fault tolerance could differ depending on the exact setup - whether information is written on all drives in real time or it is written on a single drive and afterwards mirrored on another, what amount of drives are used for the RAID, etcetera.
RAID in Shared Web Hosting
The hard drives which we use for storage with our innovative cloud web hosting platform are not the traditional HDDs, but high-speed solid-state drives (SSD). They function in RAID-Z - a special setup designed for the ZFS file system that we employ. All the content that you add to your shared web hosting account will be kept on multiple hard disks and at least 1 shall be used as a parity disk. This is a specific drive where an additional bit is added to any content copied on it. In case a disk in the RAID stops functioning, it will be replaced without any service disturbances and the data will be recovered on the new drive by recalculating its bits using the data on the parity disk plus that on the remaining disks. This is done to guarantee the integrity of the information and along with the real-time checksum validation which the ZFS file system performs on all drives, you won't ever have to concern yourself with the loss of any info no matter what.