Overview of RAID levels
RAID is the combination of several hard drives at different levels to increase capacity or security. In this practical tip, we will introduce you to the most common of these RAID levels.
The RAID technology
RAID stands for "Redundant Array of Independent Disks", ie an arrangement of multiple hard disks or SSDs. What is special here is the division of the data into blocks, which are then stored in a distributed manner on the different storage media.
- The three most important RAID levels are RAID 0, RAID 1 and RAID 5. We explain these in the next sections.
Split the data into RAID 0
No data is saved twice in RAID 0. The data blocks are distributed evenly over all hard disks involved.
- This allows you to use the entire storage space of all disks, while the access speed increases significantly due to a multitude of read and write options. For the user, the RAID array works like a single large hard disk.
- However, RAID 0 does not have a reduced probability of failure, which is otherwise what makes RAID. The data is not saved redundantly.
Mirroring data with RAID 1
For RAID 1 you need at least 2 hard drives. All data is stored on all hard drives, so the capacity of the entire association is based on the capacity of the smallest hard drive involved.
- RAID 1 is characterized above all by a high level of security. The probability of failure of the entire system is extremely low, since all data is available twice. RAID 1 does not increase capacity, but the read speed is increased.
RAID 5 as a combination of security and size increase
At least 3 hard drives are required for RAID 5. 2 of the hard disks then store one data block each, the third only stores a security sum, the so-called parity information. These roles are reassigned for each data block so that the security sums are distributed evenly over all hard disks.
- From them and the memory of the other hard disk, all data of a possibly failing disk can be recalculated. This works with any number of hard drives. Data security is guaranteed as long as no more than one hard drive fails at the same time.
- With 3 hard drives with one TB each, you could store 2 TB data in the RAID 5 system. 1 TB would be required for the security sums.
You can read more about the difference between software or hardware RAID in another practical tip.