RAID types
QTS supports several RAID types. Each type provides a different combination of performance and redundancy.
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For best performance and space efficiency, you should use disks of the same brand and capacity when creating a RAID group.
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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.
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Create a separate RAID group for each capacity.
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Combine the RAID groups using storage pools.
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If different types of disk (HDD, SSD, SAS) are combined in one RAID group, the RAID group will function according to the speed of the slowest disk.
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Increasing the number of disks in a RAID group increases the risk of simultaneous disk failure and lengthens rebuild times. For example, a RAID group with 24 drives is 20 times more likely to fail with RAID 6 than with RAID 60. When creating a storage pool with a large number of disks, you should split the disks into sub-groups using RAID 50 or RAID 60.
RAID Type |
Number of Disks |
Disk Failure Tolerance |
Capacity |
Overview |
---|---|---|---|---|
Single |
1 |
0 |
Total disk capacity |
|
JBOD (just a bunch of disks) |
≥ 2 |
0 |
Total combined disk capacity |
|
RAID 0 |
2 to 16 |
0 |
Total combined disk capacity |
|
RAID 1 |
2 |
1 |
Half of the total combined disk capacity |
|
RAID 5 |
3 to 16 |
1 |
Total combined disk capacity minus 1 disk |
|
RAID 6 |
4 to 16 |
2 |
Total combined disk capacity minus 2 disks |
|
RAID 10 |
4 to 16 (Must be an even number) |
1 per pair of disks |
Half of the total combined disk capacity |
|
RAID 50 |
6 to 30 (Must be an even number) |
1 per disk subgroup |
Total combined disk capacity minus 1 disk per subgroup |
|
RAID 60 |
8 to 30 (Must be an even number) |
2 per disk subgroup |
Total combined disk capacity minus 2 disks per subgroup |
|