Redundant Array of Independent Disks, or RAID, is a method of saving content on a number of hard disks simultaneously. A RAID can be software or hardware based on the hard drives that are used - physical or logical ones, yet what is common between them is that they all work as one single unit where info is kept. The key advantage of using a RAID is redundancy as the data on all the drives will be identical all of the time, so even if some drive fails for some reason, the data will still be present on the remaining drives. The general performance is also enhanced because the reading and writing processes could be split between different drives, so a single one won't be overloaded. There are different types of RAIDs where the efficiency and fault tolerance could differ based on the particular setup - whether your data is written on all drives in real time or it's written on one drive and after that mirrored on another, what number of drives are used for the RAID, and so on.
RAID in Cloud Hosting
The hard drives that we employ for storage with our state-of-the-art cloud web hosting platform are not the standard HDDs, but fast solid-state drives (SSD). They function in RAID-Z - a special setup intended for the ZFS file system that we use. All the content that you upload to your cloud hosting account will be saved on multiple hard disks and at least 1 shall be employed as a parity disk. This is a specific drive where an extra bit is included to any content copied on it. If a disk in the RAID stops working, it'll be replaced with no service disturbances and the info will be rebuilt on the new drive by recalculating its bits thanks to the data on the parity disk plus that on the remaining disks. This is done to ensure the integrity of the data and along with the real-time checksum authentication which the ZFS file system runs on all drives, you won't ever have to concern yourself with the loss of any information no matter what.