Home > Storage > Unity XT > Storage Admin > Dell Unity: Best Practices Guide > Dynamic Pools
Dynamic Storage Pools apply RAID protection to groups of drive extents from drives within the pool and allow for greater flexibility in managing and expanding the pool. Dynamic pools where first made available for Unity all-flash systems running Dell UnityOS 4.2 and later. Dynamic pool support has been extended to Unity Hybrid flash systems with the release of Dell UnityOS 5.2 and later.
At the time of creation, dynamic pools will use the largest RAID width possible with the number of drives specified, up to the following maximum widths:
With dynamic pools, there is no performance or availability advantage to smaller RAID widths. Therefore, to maximize usable capacity with parity RAID, it is recommended to initially create the pool with enough drives to guarantee the largest possible RAID width.
Hot spares are not needed with dynamic pools. A dynamic pool will automatically reserve spare space in the pool at a rate of 1 drive’s worth of capacity per every 32 drives. In the event of a drive failure, the data that was on the failed drive is rebuilt into the spare capacity on the other drives in the pool. Additionally, un-bound drives of the appropriate type can be used to replenish a pool’s spare capacity, after the pool rebuild has occurred.
Dell Unity supports two types of storage objects, thin or thick.
By default, Dell Unity creates thin storage objects. Thin storage objects are virtually provisioned and space efficient. In general, Dell Technologies recommends using thin storage objects, as they provide the best capacity utilization, and are required for most features. Thin storage objects are recommended when any of the following features will be used:
Thick storage objects will reserve capacity from the storage pool, and dedicate it to that particular storage object. Thick storage objects guarantee that all advertised capacity is available for that object. Thick storage objects are not space efficient, and therefore do not support the use of space-efficient features. If it is required to enable a space-efficient feature on a thick storage object, it is recommended to first migrate the thick storage object to a thin storage object, and enable the feature during the migration (for Data Reduction) or after migration has completed (for Snapshots, Thin Clones, and Asynchronous Replication).
In addition to capacity for storing data, storage objects also require pool capacity for metadata overhead. The overhead percentage is greater on smaller storage objects. For better capacity utilization, Dell Technologies recommends configuring storage objects that are at least 100GB in size, and preferably at least 1TB in size.