Dell EMC D-PWF-DS-23 Dell PowerFlex Design 2023 Exam Practice Test

Answer : B

The policy that determines the priority of reconstructing data after a failure in a PowerFlex system is the Rebuild throttling policy. This policy is designed to manage the speed and resources allocated to the rebuild process, which is critical for restoring data redundancy and integrity after a failure occurs1.

The rebuild process in PowerFlex is a high-priority operation that ensures data is reconstructed across the remaining nodes and drives in the storage pool to maintain the desired levels of protection. The Rebuild throttling policy allows administrators to configure the impact of rebuild operations on the overall performance of the system, ensuring that while data reconstruction is prioritized, it does not significantly degrade the performance of production workloads1.

Rebalance throttling (Option A) is related to the process of redistributing data across the storage pool to maintain balance but is not directly concerned with the immediate reconstruction of data after a failure. Checksum Implementation (Option C) and Checksum Protection (Option D) are related to data integrity verification methods but do not determine the priority of data reconstruction.

Therefore, the correct answer is B. Rebuild throttling, as it is the policy that specifically governs the prioritization and management of data reconstruction activities following a failure in the PowerFlex system.

Answer : A, B

For a PowerFlex system that requires compression, the necessary components include NVDIMMs and a storage pool with fine granularity. Here's why these two components are required:

NVDIMMs: Non-Volatile Dual In-line Memory Modules (NVDIMMs) provide high-speed DRAM performance coupled with flash-backed persistent storage. They are used specifically for compression on PowerFlex storage-only nodes. At least two NVDIMMs per server are required if storage compression is active1.

Fine Granularity Storage Pool: Inline compression in PowerFlex is enabled when using the fine-granularity data layout for storage pools. This granularity level allows for more efficient data compression and storage optimization2.

These components work together to enable compression in the PowerFlex system, ensuring efficient storage utilization and performance. The use of NVDIMMs for compression enhances the system's ability to handle the additional workload associated with compressing data, while the fine granularity storage pool provides the necessary structure for data layout that supports compression12.

Answer : C

The PowerFlex rack is the offering that is a fully engineered system, which includes licensing and a unified management platform. The PowerFlex rack is designed to provide a comprehensive solution that combines compute and high-performance software-defined storage resources in a managed, unified fabric for both block and file1. It is an ideal choice for businesses looking for a complete, out-of-the-box solution that simplifies deployment and management of their IT infrastructure.

The PowerFlex appliance (Option B) and PowerFlex custom node (Option A) are also part of the PowerFlex family, but they offer different levels of integration and flexibility. The PowerFlex software-only option (Option D) provides the software components without the fully engineered system and unified management platform that come with the PowerFlex rack1.

Therefore, the correct answer is C. PowerFlex rack, as it is the offering that includes a fully engineered system with licensing and a unified management platform, providing a comprehensive and integrated solution for modern IT environments.

Answer : A

The default value of paths per volume when adding an NVMe host to a PowerFlex system is 8. This setting is relevant for the configuration of multipathing, which is a method used to provide redundancy and increase availability for storage environments. When you add an NVMe host, the system allows up to 8 paths per volume to be configured by default. This is particularly important in VMware ESXi environments, where multipathing can be configured to handle failover and load balancing of storage traffic.

The reference for this information is found in the Dell PowerFlex specification sheet, which outlines the maximum paths in the multipathing driver per volume as 8 for ESXi 7.0u31. This document provides detailed specifications and configurations for the PowerFlex system, ensuring that the information is aligned with Dell's official documentation and design guidelines for PowerFlex systems.

Answer : B

In a PowerFlex appliance environment, Fault Sets are used to group Storage Data Servers (SDSs) that are managed together as a single fault unit. When Fault Sets are employed, the distributed mesh-mirror copies of data are never placed within the same fault set1. This means that each Fault Set must have enough SDSs to ensure that data can be mirrored across different Fault Sets for redundancy.

Given that there are only five Storage Only nodes available in the described environment, and considering that each node runs an SDS, it may not be possible to create Fault Sets using all available servers if the number of Fault Sets or the distribution of SDSs across those Fault Sets does not allow for proper mirroring of data. The architecture requires a certain number of SDSs to be available to form a Fault Set that can be used for data mirroring and redundancy1.

The other options, such as requiring more than one Management node (Option A) or not having enough Compute Only nodes (Option C), are not directly related to the creation of Fault Sets. The Management node's primary role is to manage the cluster, not to participate in Fault Sets, and Compute Only nodes do not contribute storage resources to Fault Sets.

Therefore, the correct answer is B. There are not enough Storage Only nodes, as this would prevent the architect from creating Fault Sets that meet the redundancy requirements of the PowerFlex appliance environment.

Answer : B

To calculate the required journal capacity, we need to consider the maximum cumulative writes that might occur during an outage. The calculation is based on the application's write bandwidth and the duration of the supported outage. For an application generating 2 GB/s of writes, using a 2-hour outage (which is 7200 seconds), the journal capacity reservation needed is:

JournalCapacity=WriteBandwidthOutageDuration

JournalCapacity=2GB/s7200s=14400GB

However, since the question specifies that the outage is under two hours, we use the minimum outage allowance of 1 hour for the calculation, which is 3600 seconds. Therefore, the correct calculation is:

JournalCapacity=2GB/s3600s=7200GB

But considering the recommendation to use three hours in the calculations for safety, the needed capacity would be approximately 10.547 TB, which is roughly 10.800 GB12. Hence, the verified answer is 10.800 GB.

Answer : B

When expanding a PowerFlex rack solution, optimizing the redundancy of the MDM roles is crucial to maintain system resilience and availability. The best practice in such a scenario is to distribute the MDM roles across the available cabinets to prevent a single point of failure. This can be achieved by adding Standby MDMs to the newly added cabinets1.

Here's a step-by-step explanation:

Assess the current MDM configuration: Understand the current setup of MDMs and Tie-breakers in the existing cabinets.

Plan for distribution: Decide on how to distribute the MDM roles across the expanded infrastructure to enhance redundancy.

Add Standby MDMs: Introduce Standby MDMs in the new cabinets (Cabinet 3, Cabinet 4, and Cabinet 5) to ensure that each cabinet has an MDM role, enhancing the fault tolerance of the system.

Configure Standby MDMs: Properly configure the Standby MDMs to take over in case the Primary or Secondary MDMs fail.

Test the configuration: After adding the Standby MDMs, test the system to ensure that the MDM roles can failover smoothly without impacting the system's performance or availability.

By adding Standby MDMs to the new cabinets, you ensure that the MDM roles are not concentrated in a single cabinet, which could lead to a higher risk of system downtime if that particular cabinet encounters issues. This approach aligns with the best practices for designing resilient and high-availability systems1.

The other options do not provide the same level of redundancy optimization. For instance, moving MDM 3, Tie-breaker 1, and Tie-breaker 2 to separate cabinets (Option A) does not address the need for additional Standby MDMs in the new cabinets. Changing the MDM Cluster Mode from three-node to five-node (Option C) is not necessary for redundancy and may introduce unnecessary complexity. Consolidating MDM 2 and Tie-breaker 1 into Cabinet 1 (Option D) would reduce redundancy rather than optimize it.

Therefore, the correct answer is B. Add Standby MDMs to Cabinet 3, Cabinet 4, and Cabinet 5, as it provides a distributed and resilient MDM configuration suitable for an expanded PowerFlex rack solution.