Home > Storage > Unity XT > Storage Admin > Dell Unity Dynamic Pools > Minimum drive counts
When creating a dynamic pool, there is a minimum number of drives that need to be selected for each tier to create the pool. This number directly depends on the RAID type selected for each tier, and a warning will be provided if the minimum drive count is not satisfied.
Table 2 shows the relationship between the RAID type, the stripe width, and the minimum number of drives. This table only shows the smallest stripe widths supported, and the minimum number of drives it takes to create them. As an example, the smallest RAID 5 stripe width the system supports is a 4+1. The smallest drive tier created with the RAID 5 4+1 configuration is 6 drives. The minimum drive count includes the number of drives specified in the stripe width, plus the hot spare capacity. The hot spare capacity is selected by the user at pool creation or when expanding the pool with a new drive tier and can either be set to 1 or 2 drives for every 32 drives in the pool.
Table 2 Dynamic pool minimum drive counts at creation.
RAID type | Stripe width | Minimum number of drives | How it is calculated |
RAID 5 | 4+1 | 6 | (4+1) + hot spare capacity |
RAID 6 | 4+2 | 7 | (4+2) + hot spare capacity |
RAID 1/0 | 1+1 | 3 | (1+1) + hot spare capacity |