RAID, or Redundant Array of Independent Disks, is a technology for saving data on a number hard disks which function together as a single logical unit. The drives could be physical or logical i.e. in the aforementioned case one drive is divided into independent ones through virtualization software. Either way, exactly the same info is kept on all the drives and the main advantage of using this type of a setup is that in case a drive fails, the data will still be available on the remaining ones. Having a RAID also improves the performance because the input and output operations will be spread among a couple of drives. There are several kinds of RAID dependant upon how many hard drives are used, whether writing is carried out on all the drives in real time or just on one, and how the info is synchronized between the hard drives - whether it is recorded in blocks on one drive after another or it is mirrored from one on the others. All these factors indicate that the error tolerance and the performance between the various RAID types may differ.
RAID in Hosting
Our state-of-the-art cloud web hosting platform where all hosting accounts are made uses super fast SSD drives instead of the classic HDDs, and they work in RAID-Z. With this setup, several hard drives operate together and at least one of them is a dedicated parity disk. Basically, when data is written on the other drives, it's copied on the parity one adding an extra bit. This is performed for redundancy as even if some drive fails or falls out of the RAID for some reason, the info can be rebuilt and verified thanks to the parity disk and the data recorded on the other ones, thus not a single thing will be lost and there will not be any service interruptions. This is one more level of security for your info along with the state-of-the-art ZFS file system which uses checksums to guarantee that all of the data on our servers is undamaged and is not silently corrupted.