Comparing RAID 0, 1, 5, 6 and 10

RAID (Redundant Array of Independent Disks) combines two or more hard disk drives into a single unit, with the benefits varying depending on the RAID level the user opts for. What is the difference between RAID 0, 1, 5 and 10?

RAID 0 – or disk striping - is essentially the basic RAID level, and offers the user increased speed, capacity and performance. Data is striped across two or more hard disk drives, offering at least double the storage space. As well as increasing storage space, RAID 0 offers at least double the read/write speeds, as multiple read/write heads are in operation. However, RAID 0 offers no fault tolerance and no redundancy, meaning if one drive fails, it breaks the array, resulting in data loss. Since protection from data loss is one of the main reasons users opt for RAID systems, this is a major drawback.

RAID 1 – or disk mirroring – reads and writes an exact copy of data to two or more drives, though it is typically two. Data can be read very fast due to two or more sets of heads being in operation simultaneously, but write speeds are slower, as data needs to be written to each disk in the array. All the drives in the array contain the exact same data, so all drives but one can fail and the data will still be accessible. Once a fault disk is replaced, the data is then copies from the remaining functional disk to the new drive. However, RAID 1 only offers the storage capacity of one drive, and results in a higher cost per gigabyte.

RAID 5 – or striping with parity – stripes data across multiple disks, in the same way as RAID 0. However, it also stores parity data, which is stored on about one third of the total available disk space. Parity information is a small amount of data that can describe a larger amount, aiding in the rebuilding of data following a crash. This essentially means that RAID 5 is the best of RAID 0 and RAID 1 combined, offering increased speed, capacity and redundancy. However, RAID 5 requires at least three drives. If any of the disks in the array fails, the data is recreated using the parity information. RAID 6 – or striping with double parity – is similar to RAID 5, but it stores an extra parity block. This means that two drives can fail at once without breaking the array. RAID 6 requires at least four hard drives.

RAID 10 – or striping and mirroring – combines the mirroring of RAID 1 with the striping of RAID 0, giving the user increased redundancy and performance. Requiring a minimum of four hard drives, RAID 10 stripes data across mirrored pairs, and as long as one disk in each pair is functional, the data can be accessed. If two disks in the same pair fail, then the data will be lost because there is no parity.

It should be noted, however, that while RAID provides data redundancy that protects your data in the event of a hardware failure, it is not a logical backup. Your data can still be lost through human error, file corruption or malware. For this reason, whatever RAID level you choose, we recommend always backing up your data regularly. If you require assistance getting your data back from a RAID system, our RAID data recovery team will be happy to help. 

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