RAID Types

QTS supports several RAID types. Each type provides a different combination of striping and redundancy.

Important:

If disks with different capacities are combined in one RAID group, all disks function according to the capacity of the smallest disk. For example, if a RAID group contains five 2 TB disks and one 1 TB disk, QTS detects six 1 TB disks.

QNAP recommends the following when mixing disks of different capacities.
- Create a separate RAID group for each capacity.
- Combine the RAID groups using storage pools.
Using only one disk type (HDD, SSD, SAS) in a RAID group is recommended. If different types of disk are combined in one RAID group, the RAID group will function according to the speed of the slowest disk.

RAID Type	Number of Disks	Disk Failure Tolerance	Capacity	Overview
Single	1	0	Total disk capacity	Uses a single disk for storage. Provides no disk failure protection or performance benefits. Suitable for single disk configurations that have a data backup plan in place.
JBOD (just a bunch of disks)	1 or more	0	Total combined disk capacity	Combines disks together in a linear fashion. QTS writes data to a disk until it is full before writing to the next disk. Uses the total capacity of all the disks. Not a real RAID type. It provides no disk failure protection or performance benefits. Unless you have a specific reason to use JBOD, RAID 0 should be used instead.
RAID 0	2 or more	0	Total combined disk capacity	Disks are combined together using striping. RAID 0 offers the fastest read/write speeds and uses the total capacity of all the disks. Provides no disk failure protection. This RAID type must be paired with a data backup plan. Recommended for high performance applications such as video editing.
RAID 1	2	1	Half of the total combined disk capacity	An identical copy of data is stored on two disks. If either disk fails, data can still be read from the other disk. Half of the total disk capacity is lost, in return for a high level of data protection. Recommended for NAS devices with two disks.
RAID 5	3 or more	1	Total combined disk capacity minus 1 disk	Data and parity information are striped across all disks. One disk is used for parity. This means that if any one disk in the group fails, it can be replaced and the data on it can be restored. Striping means read speeds are increased with each additional disk. Recommended for a good balance between data protection and speed.
RAID 6	4 or more	2	Total combined disk capacity minus 2 disks	Data and parity information are striped across all disks. Same as RAID 5, but two disks are used for parity. This means that it protects against two disk failures, but the capacity of two disks are lost. Recommended for business and general storage use. It provides high disk failure protection and read performance.
RAID 10	4 or more (even number required)	1 per pair of disks	Half of the total combined disk capacity	Every two disks are paired using RAID 1 for failure protection. Then all pairs are striped together using RAID 0. Excellent random read/write speeds and high failure protection, but half the total disk capacity is lost. Recommended for application or database storage.
RAID 50	6 or more	1 per disk sub-group	Total combined disk capacity minus 1 disk per sub-group	Multiple small RAID 5 groups are striped to form one RAID 50 group. Better failure protection and faster rebuild times than RAID 5. More storage capacity than RAID 10. Better random access performance than RAID 5 if all of the disks are SSDs. Recommended for enterprise backup with ten or more disks.
RAID 60	8 or more	2 per disk sub-group	Total combined disk capacity minus 2 disks per sub-group	Multiple small RAID 6 groups are striped to form one RAID 60 group. Better failure protection and faster rebuild time than RAID 6. More storage capacity than RAID 10. Better random access performance than RAID 6 if all of the disks are SSDs. Recommended for business storage and online video editing with twelve or more disks.