DEE-1111 Exam Dumps - Expert - PowerMax and VMAX All Flash Solutions

 In a SRDF/Metro deployment in a clustered host configuration, when the RDF link state is partitioned and the R1 side has full read/write capability to the application, the R2 device also has full read/write capability to the application. With SRDF/Metro, both R1 and R2 devices may then appear as a single virtual device across the two SRDF paired arrays for host presentation. With both the R1 and R2 devices being accessible, the host or hosts (in the case of a cluster) can read and write to both R1 and R2 devices with SRDF/Metro ensuring that each copy remains current, consistent, and addressing any write conflicts which may occur between the paired SRDF devices23. References: Dell EMC PowerMax and VMAX All Flash: SRDF/Metro Overview and Best Practices, Deploying Dell EMC SRDF/Metro Smart DR with Microsoft SQL Server for Physical and Virtual Environments

An SRDF/Metro device pair was in an ActiveActive state, meaning that both the R1 and R2 devices were read/write accessible to the host or hosts. A link failure between arrays occurs, causing the device pair to become Not Ready (NR) on the SRDF link. SRDF/Metro responds by making the non-biased or R2 paired device inaccessible (not ready) to the host or host cluster, while keeping the biased or R1 paired device accessible (ready). This ensures that there is no data inconsistency or split-brain scenario between the two sites. The device pair enters an Active Bias state, which indicates that only one side of the pair is active and has a bias attribute set. The bias attribute determines which side of the pair remains accessible in case of a link failure. By default, the bias is set to the R1 side of the pair, but it can be changed using the symrdf set bias command. The application continues running on the R1 side, and the link failure is addressed. Once the link is restored, the device pair resumes the ActiveActive state and both devices become accessible again.

References:

• SRDF/Metro overview
• VMware vSphere Metro Storage Cluster (vMSC) with Dell PowerMax and Dell EMC VMAX SRDF/Metro
• Understanding bias

An application owner is experiencing performance issues for their application. Unisphere for PowerMax is showing the storage group is compliant with the current Service Level. A Service Level is a predefined set of performance attributes that can be applied to a storage group to ensure consistent and predictable performance. A Service Level specifies a target response time, an upper response time limit, and a lower response time limit for the storage group. If the application owner wants to improve theperformance of their application, they can adjust the Service Level to a higher level of service, which will provide lower response times and higher priority for the storage group. Unisphere for PowerMax provides five predefined Service Levels: Diamond, Platinum, Gold, Silver, and Bronze, as well as an Optimized option that automatically adjusts the Service Level based on workload characteristics. The application owner can choose a higher Service Level from these options or create a custom Service Level with their own performance parameters.

References:

• Dell EMC PowerMax: Service Levels for PowerMaxOS
• Dell Unisphere for PowerMax 10.0.0 Product Guide

Unisphere for PowerMax and Solutions Enabler have different ways of managing user permissions. Unisphere has a more explicit authentication mechanism for users, where each user must have a username and password to log in to the Unisphere interface. Unisphere also supports role-based access control (RBAC), where each user can be assigned one or more roles that define their level of access to the storage system resources and operations. Unisphere maintains the user and role information in a symauth database, which can be shared with Solutions Enabler. Solutions Enabler, on the other hand, uses the operating system user credentials to authenticate users. Solutions Enabler does not require users to have a username and password to run commands, but it checks the symauth database to verify if the user has the appropriate role to perform the requested operation. Solutions Enabler also supports RBAC, where each user can be assigned up to four roles that define their level of access to the storage system resources and operations.

References:

• Unisphere for PowerMax User Management
• Solutions Enabler User Management

The correct answer is D. When an SRDF/A MSC trip event occurs, the Receive Delta Set on the target arrays is checked for completeness. If the Receive Delta Set is incomplete on any of the target arrays, the session is marked as Cleanup required. This means that the data on the target arrays is not consistent and needs to be cleaned up before resuming SRDF/A replication. The symstar cleanup command can be used to discard the incomplete Receive Delta Set data and resume SRDF/A replication from the last consistent point1

A noisy neighbor issue occurs when one or more applications consume more resources than expected, causing performance degradation for other applications. This can affect the SL compliance of a storage group, as the service level defines the expected response time and performance for the applications in that group. If a noisy neighbor consumes too much cache, bandwidth, or CPU cycles, it can cause the SL compliance to drop below the target level. Therefore, answer A is correct.

B, C, and D are incorrect because they are not likely to cause SL compliance impact for a storage group. Queue depth full event (B) is a host-side issue that occurs when the host queue depth is too low or the host I/O rate is too high, causing the host to stop sending I/O requests to the array. Host queue depth setting © is also a host-side parameter that determines how many I/O requests can be queued by the host. Performance thresholds (D) are user-defined values that trigger alerts when certain metrics exceed or fall below the specified levels. None of these factors affect the SL compliance of a storage group on the array.

In an SRDF/Metro Smart DR configuration, the Fault-Aware Witness gives a higher priority to Bias when selecting the winning array. The bias settings for the devices are used to determine the preferred winner in the event of a failure2. The preferred winner is the side that has priority when requesting the lock from the witness instance2. References: Dell EMC PowerMax and VMAX All Flash: SRDF/Metro Overview and Best Practices

The symauth command is used to manage user authorization for SYMCLI commands. The exhibit shows the output of the symauth -list command, which displays the user groups and access types defined for SYMCLI commands. The output shows that there are two user groups: AdminGrp and EmcMgmtGrp. The AdminGrp group has ADMINRD access type, which means that users in this group can run any SYMCLI command with read-only access. The EmcMgmtGrp group has BASECONTROL access type, which means that users in this group can run only a subset of SYMCLI commands with read/write access. Therefore, the correct description of a possible configuration created by SYMACL is hosts that are part of AdminGrp group2

the maximum number of SCM RAID groups that can be added to a two-engine PowerMax 2000 would depend on various factors including the specific configuration of the system and the capacity requirements.

In a Concurrent SRDF/Star configuration failure, the first step to recover is to switch to the 1st Target Site. This is because in a Concurrent SRDF/Star configuration, there are two target sites and one source site. If there’s a failure, the source site can switch to either of the target sites based on the business continuity plan1. References: Dell EMC Solutions Enabler 9.2 SRDF Family CLI User Guide

The -precopy option in the relink command can be used when you want to start copying data to the target devices immediately after the link operation. This can be useful in situations where additional volumes have been added, increasing the link to full copy time. By using -precopy, you ensure that the data starts copying immediately, preventing potential issues.

The metrics that are recommended to start analyzing the overall efficiency of the array due to cache are array-level % Hit and % Cache WP. The array-level % Hit metric shows the percentage of read requests that are satisfied from the cache memory, without accessing the physical disks. A high % Hit value indicates that the cache is effective in reducing the read latency and improving the performance. The % Cache WP metric shows the percentage of cache memory that is occupied by write pending data, which is data that has been written to the cache but not yet destaged to the physical disks. A high % Cache WP value indicates that the cache is under pressure and may not have enough space to accommodate new write requests, which can lead to performance degradation. By monitoring these two metrics, a storage administrator can evaluate the overall efficiency of the array due to cache and identify any potential issues or bottlenecks.

References:

• System efficiency overview | Dell PowerMax: Data Reduction | Dell Technologies Info Hub
• Metrics (PowerMax & VMAX) - VMware Docs
• Dell EMC PowerMax storage
• Replication cache | Dell EMC PowerMax and VMAX All Flash: TimeFinder SnapVX Local Replication

 In an SRDF/Metro configuration with bias setting, if there is a failure at the R1 array (which is configured as the bias side), the R2 device automatically becomes the active device. This means that even if there’s a failure on the R1 side, operations can continue on the R2 side without interruption, ensuring high availability.

https://infohub.delltechnologies.com/l/dell-emc-powermax-and-vmax-all-flash-srdf-metro-overview-and-best-practices-1/understanding-bias