Dell Unity XT dynamic pools are designed with flexibility for expansion. When adding new drives to an existing dynamic pool, the system supports mixing drives of different sizes, provided they are of the same type (e.g., all SSDs). The underlying architecture of dynamic pools divides all physical drive space into small, manageable extents. This allows the system to aggregate the total capacity from all drives, meaning the full capacity of the new, larger 3.84 TB drives will be added to the pool's usable capacity without being truncated to match the size of the original drives.

B. Only half of the capacity of the new drives will be available.

This is incorrect. This behavior (truncating capacity to the smallest drive size) is characteristic of traditional RAID groups, not the more advanced Dell Unity dynamic pools.

C. Three of the drives will be added with a fourth reserved as spare.

This is incorrect. Dynamic pools utilize a distributed sparing model where spare capacity is reserved across all drives in the pool, rather than dedicating an entire drive as a hot spare.

D. The mixing of drive types is not supported, and the operation will fail.

This is incorrect. Mixing drive sizes within the same technology type (e.g., SAS SSD) is a supported and documented feature for expanding dynamic pools on Dell Unity XT systems.

1. Dell Unity: Dynamic Pools White Paper (H15093.7)

Page 13, Section: Pool Expansion: "Drives of different sizes can be added to the pool, and the full capacity of the new drives is available for use. This is because the entire pool is virtualized, and all drive space is broken down into small extents. This allows the system to use all the space on all the drives, regardless of their size." This directly supports answer A and refutes B and D.

Page 10, Section: Sparing: "Dynamic pools utilize a distributed sparing technology... Instead of dedicating entire drives to be on standby in case of a failure, spare space is distributed across all the drives in the dynamic pool." This refutes answer C.

2. Dell Unity Family Unisphere Online Help (Version 5.3)

Section: Add storage to a pool: The documentation outlines the process for expanding a pool and lists the compatibility rules. It states, "For dynamic pools, you can add drives of a different size than the drives that are already in the pool, as long as the new drives are of the same drive technology." This confirms that the operation is supported, refuting option D.