What is the use of RAID
What is a RAID system?
RAID stands for Redundant Array of Independent Disks. A RAID system is a combination of several hard drives in which data is stored (except for RAID 0) in such a way that it is protected against loss. The hard disks should be identical in size and type. In the following we explain the advantages and disadvantages of the most important RAID systems so that you can choose the right one.
* Single disc (from one hard drive): This mode is not a RAID system. Each hard drive is used individually as a drive. If one fails, the data is gone too. The other discs are not affected.
* JBOD (from two hard disks): In this network, several hard drives are combined into one large drive. If one breaks, all disks are affected. For this reason, JBOD is not recommended.
* RAID 0 (from two hard disks): Several hard disks are also connected in this RAID mode, although the focus is on speed. If you save a file, it will be distributed to the various hard drives. This means that the hard disks can work in parallel and access the data more quickly. While a RAID 0 system in the computer can be useful, it is of little use in a NAS: The network slows down the gain in speed. Even with a RAID 0 system, all data is lost if one hard drive in the network fails.
* RAID 1 (from two hard disks): With RAID 1, data security is in the foreground. All data is saved twice so that the same data is stored on two hard drives. This means that you only have half of the actual storage space available, but your data is protected. If one of the hard drives fails, the NAS automatically reads from the other hard drive. In the meantime, the defective hard disk can be replaced. Despite this security, a RAID only protects your data to a limited extent. Be sure to read the tip "RAID does not replace a backup".
* RAID 5 (from three hard disks): In a RAID 5 network, the data is also protected against the failure of a hard drive - however, you lose less storage space and a little more speed than with RAID 1. While with the former only half of the storage space is used, with RAID 5 it is that Number of hard drives minus one. For example, if you use four 500 GB hard disks, you may need 1500 GB as storage. The rest is reserved for data backup. It doesn't matter which hard drive fails. However, if two hard drives fail at the same time, the data is lost. Defective hard disks should therefore be replaced immediately. This is necessary anyway, since the network will still work reliably but slowly in the event of a failure. For a NAS with three hard drives or more, RAID 5 is often the best solution.
* RAID 5 + Spare (from four hard disks): This mode corresponds to the previous one, with a hard disk being used as a reserve. So you lose the storage space of two hard disks. To do this, the actual RAID 5 network is immediately reconstructed in the event of a failure. During this phase, however, the data is not protected in the event of a further failure.
* RAID 6 (four or more hard disks): With RAID 6, two hard drives are used for backup, so you lose the same amount of space as with RAID 5 + Spare. RAID 6 is somewhat slower due to the higher complexity, but the simultaneous failure of two hard disks can also be coped with.
Tip: RAID does not replace a backup
A RAID system - with the exception of RAID 0 - protects against hard drive failure, but backups are necessary for your important data. Because with the secure storage of the data, a RAID system is not armed against software errors. If you catch a destructive virus or if a file is saved incorrectly due to a program error, RAID is of no avail. The data simply ends up incorrectly several times on the hard disk. Accidentally deleted data can also no longer be saved by a RAID. Therefore, a regular backup is mandatory even with a RAID system.
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