EMC DEE-1111 Expert - PowerMax and VMAX All Flash Solutions Exam Practice Test

SRDF device used for Concurrent SRDF environments =R21

SRDF device used for SRDF/Star environments =R11

SRDF device used for Cascaded SRDF environments =R22

A dual personality SRDF device is a device that can act as both an R1 and an R2 device in different SRDF configurations. There are three types of dual personality SRDF devices: R21, R11, and R22.

• An R21 device is an R2 device that is paired with another R1 device in a different SRDF group. This allows the R21 device to receive updates from the primary site and send updates to the secondary site. An R21 device is used for Concurrent SRDF environments, which provide simultaneous disaster recovery and data migration capabilities.For example, an R21 device can be used to migrate data from one array to another while maintaining a synchronous copy of the data on a third array.1
• An R11 device is an R1 device that is paired with another R1 device in a different SRDF group. This allows the R11 device to receive updates from the primary site and send updates to the tertiary site. An R11 device is used for SRDF/Star environments, which provide three-site disaster recovery capabilities with a single hop between any two sites.For example, an R11 device can be used to create a synchronous copy of the data on a secondary site and an asynchronous copy of the data on a tertiary site.2
• An R22 device is an R2 device that is paired with another R2 device in a different SRDF group. This allows the R22 device to receive updates from the secondary site and send updates to the tertiary site. An R22 device is used for Cascaded SRDF environments, which provide three-site disaster recovery capabilities with two hops between the primary and tertiary sites.For example, an R22 device can be used to create an asynchronous copy of the data on a secondary site and another asynchronous copy of the data on a tertiary site.3

References:

• Dell EMC SRDF Introduction - Dell Technologies Partner Portal
• Dell EMC PowerMax and VMAX All Flash: SRDF Product Guide
• Dell EMC PowerMaxOS Performance Guide

 In PowerMax, each RAID group is divided into 64 logical blocks known as TDATs (Thin Device Addressable Tracks). Each TDAT is configured to hold data at a given data reduction level, from 1:1 uncompressed data all the way to 16:11. References: Data Protection Schemes | Dell PowerMax: Reliability, Availability, and Serviceability | Dell Technologies Info Hub

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 commands2

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.

If an administrator implemented SYMACLs on a PowerMax using host-based Access IDs and is no longer able to run SYMCLI commands against the volumes belonging to a host, one possible reason could be that the SYMAPI options file was manually modified with the wrong host ID. The SYMAPI options file contains configuration settings for Solutions Enabler, including host IDs for access control. If this file is incorrectly modified, it could prevent the administrator from running SYMCLI commands against certain volumes34. References: Dell EMC PowerMax and VMAX All Flash: Embedded Management, Role Based Access Control on PowerMax – Storage Intelligence

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 request1.
• 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 director2.
• 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 engine2.
• 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 disk2.
• 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 requests2.
• 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 priority2.

The steps in sequence as part of key management for a drive failure on a PowerMax array are as follows:

• Spare drive invoked against failed drive. This step involves the system automatically selecting a spare drive and starting the sparing operation to rebuild the data from the failed drive.The spare drive is encrypted with a temporary key that is stored in the embedded key manager.1
• 1st entry in audit log.This step involves the system logging the sparing operation and the temporary key generation in the audit log, which records all key management activities and events.1
• Sparing operation is completed. This step involves the system completing the data rebuild and marking the spare drive as a permanent replacement for the failed drive.The spare drive becomes part of the RAID group and inherits the same properties as the failed drive.1
• Key is deleted from the repository when failed drive is removed. This step involves the system deleting the Data Encryption Key (DEK) of the failed drive from the embedded key manager when the failed drive is physically removed from the array.The DEK is a unique 256-bit AES-XTS key that is used to encrypt and decrypt data on each drive.1
• 2nd entry in audit log.This step involves the system logging the DEK deletion and the failed drive removal in the audit log.1
• Key is generated for the replacement drive when installed. This step involves the system generating a new DEK for the replacement drive when it is installed in the array.The new DEK is stored in the embedded key manager and used to encrypt and decrypt data on the replacement drive.1

References:

• Dell EMC PowerMax and VMAX All Flash: Data at Rest Encryption

 If an administrator has added custom SSL certificates and each time a client connection is made, default certificates are used, then ‘restart storsrvd’ must be completed. This is because changes to SSL certificates often require a restart of the service that uses them in order for the new certificates to be correctly loaded and used for future client connections1.

 When the cache space fills up, I/O will be queued until an empty cache slot is available. This is because PowerMax operates as a cache-centric architecture, where all data is passed through cache before being stored on disk. Cache is used to buffer incoming and outgoing data, as well as to support various functions such as replication and data reduction. When cache is full, the array cannot accept any more data until some cache slots are freed up by flushing data to disk or invalidating stale data. Therefore, answer B is correct.

A, C, and D are incorrect because they do not describe what happens when cache space fills up. I/O will not be serviced at the speed of the destination device (A), as this would bypass the cache and degrade performance. Cache is not permanently flushed © or temporarily disabled (D), as this would result in data loss or corruption.

 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

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

During a Non-Disruptive Migration (NDM), issuing the ReadyTgt SYMCLI command to the migrating Storage Group completes the migration by removing the migrated application resources from the source array2. This command is typically issued after all data has been synchronized from the source to the target array and application I/O has been switched to thetarget array2. References: NDM overview | Dell EMC PowerMax and VMAX: Non-Disruptive Migration Best Practices and Operational Guide | Dell Technologies Info Hub

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

The two factors that define Capacity Management are I/O capacity and storage capacity. I/O capacity refers to the ability of the system to handle the incoming and outgoing data traffic from the hosts or applications. Storage capacity refers to the amount of disk space available to store the data. Capacity Management is the process of planning, monitoring, and optimizing the use of these resources to ensure optimal performance, availability, and efficiency of the system.

References:

• Dell EMC PowerMax: Family Overview
• System Resource Usage

The symstar halt command is used to write disable devices and synchronize SRDF data to remote sites in an SRDF/Star configuration. This command ensures that all sites have a consistent copy of data before switching the workload site from one site to another. Therefore, the symstar halt command should be used before the workload switch in case of a disaster at the workload site of an SRDF/Star configuration1

 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 others34. 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