DEE-1111 Expert - PowerMax and VMAX All Flash Solutions Questions and Answers

The alert settings required are a first level warning at 10 ms and a second level critical alert at 15 ms. These settings will ensure that high I/O response times for a specific storage group are tracked and appropriate actions are taken when the response times exceed the specified thresholds.  References:  Dell EMC PowerMax: Service Levels for PowerMaxOS

  The most likely cause of this behavior is QFULL responses of the FA ports. When additional hosts are zoned to certain front-end adapters, the FA ports may not be able to handle the increased I/O requests, resulting in QFULL responses. This can cause non-linear variations in throughput and sometimes a drop in throughput of more than 20%.  References:  Dell EMC PowerMax: Service Levels for PowerMaxOS

The correct sequence of actions that take place on a Write Miss is as follows:

Host sends requests to FE director and no cache slots are found. This happens when the cache is full or the desired cache slot is locked by another request 1 .

FE finds available slot by polling. This involves the FE director scanning the cache for an available slot or waiting for a slot to be freed by the BE director 2 .

FE sends data from host to mirrored cache locations. This involves the FE director writing the data from the host to two mirrored locations in the cache, one on each engine 2 .

FE responds to host to acknowledge successful write. This involves the FE director sending a signal to the host that the write operation is completed, even though the data is not yet written to disk 2 .

BE destages data as a high-priority task to make slots available. This involves the BE director flushing some of the existing write pending data from the cache to the disk, in order to free up some cache slots for new write requests 2 .

BE destages new data to disk at a later time. This involves the BE director writing the new data from the cache to the disk, according to the destaging algorithm and priority 2 .

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 group 2

When vWitness and Array Witness options are deployed in the same operating environment simultaneously, SRDF/Metro favors the Witness option over the Array Witness option. This is because the Witness option provides a higher level of protection against split-brain scenarios and data loss than the Array Witness option. The Witness option uses a third-party server to monitor the health and connectivity of both SRDF/Metro arrays and to arbitrate in case of a failure. The Array Witness option uses a third array to store configuration information and to arbitrate in case of a failure. However, the Array Witness option does not monitor the health and connectivity of both SRDF/Metro arrays, and it requires manual intervention to resume SRDF/Metro replication after a failure.

The user has been assigned the RemoteRep role only.  The RemoteRep role allows users to create, manage, and delete SRDF device pairs, as well as view array information, masking objects, device information, and RBAC rules 2 . However, it does not allow users to create and delete SRDF groups, which requires the StorageAdmin role. Therefore, answer C is correct.

A, B, and D are incorrect because they do not match the user’s profile.  SecurityAdmin (A) role allows users to manage security settings such as authentication methods, certificates, RBAC rules, and audit logs 2 .  Auditor (B) role allows users to view array information and audit logs only 2 .  LocalRep (D) role allows users to create, manage, and delete TimeFinder SnapVX sessions from a source device 2 . None of these roles allow users to create and delete SRDF device pairs.

The symaudit -list command is used to display audit records 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. However, the output also shows that there are two exceptions for specific users: Beth and Frank. Beth has ADMINRD access type for all commands, which overrides her membership in EmcMgmtGrp group. Frank has BASECONTROL access type for all commands, which overrides his membership in AdminGrp group.  Therefore, the only user who has access to run the symaudit -list command based on the symauth output shown in the exhibit is Beth, since she has ADMINRD access type for all commands 2

R11 devices are included in a Cascaded SRDF environment.  In a cascaded SRDF configuration, the R1 device at the primary site is paired with an R11 device at the secondary site, which is then paired with an R2 device at the tertiary site 2 .  References:  NDM overview | Dell EMC PowerMax and VMAX: Non-Disruptive Migration Best Practices and Operational Guide | Dell Technologies Info Hub

The NDM Updates feature should be used to complete the migration and address the client’s concern. The NDM Updates feature is designed to help automate the process of moving applications across arrays requiring a short application downtime.  It allows application migration from a VMAX (5876) array to a VMAX3 (5977), VMAX All Flash (5978), or PowerMax (5978) array 1 .  It supports pre-sync data between arrays and then schedule downtime to do the cutover 1 .  References:  Dell EMC PowerMax and VMAX: Non-Disruptive Migration Best Practices and Operational Guide

he %Busy and Balance KPIs are the most important indicators of the BE performance on a PowerMax array. The %Busy metric shows the percentage of time that a BE director is busy processing I/O requests. A high %Busy value may indicate that the BE director is overloaded and cannot keep up with the demand. The Balance metric shows the difference in %Busy between the two BE directors in a pair. A high Balance value may indicate that the workload is not evenly distributed across the pair, which can lead to performance degradation. By monitoring these two KPIs, a storage administrator can identify and troubleshoot any potential issues with the BE performance.

References:

PowerMax Performance Troubleshooting with Unisphere - Run a real time trace at the system level

  If utilization increases by 10% for both systems A and B, where system A has a current utilization of 10% and system B has a current utilization of 70%, the response times for systems A and B would not necessarily increase linearly with utilization.  The exact impact on response times would depend on various factors including workload characteristics, system configuration, and resource contention among others 3 4 . However, without specific details on these factors, it’s not possible to provide an accurate prediction for the new response times.  References:  PowerMax and VMAX All Flash: Storage Resource Pool (SRP) Effective Used Capacity threshold alert ,  Service levels and eNAS | Dell EMC PowerMax and VMAX All Flash: eNAS Best Practices

A company plans to implement SRDF/Star, which is a three-site replication solution that provides continuous data protection and disaster recovery capabilities. It is currently using SRDF/S between their two data centers, which are located within 200 kilometers and use synchronous replication. It is setting up a third data center and wants to have at least two identical copies of its data in case of a primary site failure. The third site can be located anywhere in the world and use asynchronous replication. The condition that is needed for the connection between the first two sites and the third site is that the link must be able to transport the delta set of the Recovery Point Objective (RPO) within the company’s Recovery Time Objective (RTO). The delta set is the amount of data that has changed since the last successful replication cycle. The RPO is the maximum acceptable amount of data loss measured in time. The RTO is the maximum acceptable amount of time to restore normal operations after a disaster. The link must have enough bandwidth and latency to ensure that the delta set can be transferred within the RTO without exceeding the RPO.

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SRDF Star software uses and best practices

SRDF/STAR

Remote replication using SRDF

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 point 1