Redundant Array of Independent Disks, or RAID, is a way of saving content on multiple hard drives simultaneously. A RAID could be software or hardware depending on the drives that are used - physical or logical ones, but what is common between them is the fact that they all operate as just one single unit where information is stored. The biggest advantage of using a RAID is redundancy as the information on all drives is exactly the same all of the time, so even if a drive fails for whatever reason, the data will still be available on the other drives. The general performance will also improve because the reading and writing processes could be split between a number of drives, so a single one can't be overloaded. There're different sorts of RAIDs where the functionality and fault tolerance may differ depending on the specific setup - whether your data is written on all of the drives in real time or it's written on a single drive and then mirrored on another, the number of drives are used for the RAID, and many others.
RAID in Shared Hosting
The SSD drives that our cutting-edge cloud web hosting platform employs for storage function in RAID-Z. This kind of RAID is intended to work with the ZFS file system that runs on the platform and it employs the so-called parity disk - a specific drive where data stored on the other drives is cloned with an extra bit added to it. In case one of the disks stops functioning, your Internet sites will continue working from the other ones and after we replace the faulty one, the data that will be copied on it will be rebuilt from what is stored on the remaining drives together with the information from the parity disk. This is performed so as to be able to recalculate the bits of each file correctly and to validate the integrity of the data copied on the new drive. This is another level of security for the content that you upload to your shared hosting account together with the ZFS file system which compares a special digital fingerprint for every single file on all hard drives in real time.