D-UN-DY-23 Exam Dumps : Dell Unity Deploy 2023 Exam

A LUN is a logical unit of storage that is presented to a host as a SCSI device. A LUN is composed of one or more RAID extents, which are the smallest units of storage that can be allocated to a LUN. A RAID extent is a slice of a RAID group that is used to store user data and parity information. The size of a RAID extent depends on the RAID type and the drive type of the RAID group. For example, a RAID 5 extent on a SAS drive is 128 MB, while a RAID 6 extent on a NL-SAS drive is 256 MB. The LUN is partitioned into slices that match the size of the RAID extents, and each slice is mapped to a RAID extent from a RAID group in the storage pool. The LUN slices are distributed across multiple RAID groups to improve performance and availability. References:

• Dell EMC Unity: Storage Pools and RAID Groups
• Dell EMC Unity: LUN Management

FAST VP (Fully Automated Storage Tiering for Virtual Pools) is a feature that automatically moves data within a storage pool based on the performance requirements and access patterns of the data. FAST VP data relocation runs in the background according to a user-defined schedule and rate. The schedule determines when the data relocation starts and ends, and the rate determines how much system resources are used for the data relocation. Users can set the Fast VP data relocation rate to High, Medium, Low, or None. High means that the data relocation has the highest priority and uses the most system resources, while None means that the data relocation is disabled. Fast VP data relocation does not run at all times, but only during the scheduled window. Fast VP optimizes data placement by moving 256 MB slices between disk tiers, not 1 GB slices. Users cannot enable or disable FAST VP at the LUN level, but only at the storage pool level.

References: [Dell EMC Unity: FAST Technology Overview], [Dell EMC Unity: Storage Pools and RAID Groups]

To expand a dynamic pool, the number of drives added must be equal to or greater than the stripe width of the pool. The stripe width is the number of data drives plus the number of parity drives in a RAID group. In this case, the stripe width is 12 + 1 = 13. Therefore, the minimum number of drives needed for the pool expansion is 13. References: Dell EMC Unity: Dynamic Pools Technical White Paper1, page 8.