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

The correct sequence of steps to configure and bring up an SRDF/Star environment is as follows:

• Verify SRDF/Star control host connectivity and array settings. This step involves checking the network connectivity between the control host and the three arrays involved in the SRDF/Star configuration, as well as verifying the array settings such as RDF mode, RDF consistency, and RDF emulation. The control host is the host that runs the Solutions Enabler SYMCLI commands to manage the SRDF/Star configuration.The three arrays are the primary array, the secondary array, and the tertiary array.1
• Enable SRDF/Star configuration. This step involves enabling the SRDF/Star feature on the primary array using the symstar enable command. This command also creates a STAR control device group on the primary array, which contains a single device that acts as a control point for the SRDF/Star configuration.The STAR control device group must have a unique name and number across all arrays.1
• Add BCV devices to the SRDF/Star configuration. This step involves adding Business Continuance Volume (BCV) devices to the STAR control device group on the primary array using the symstar add bcv command. BCV devices are local copies of data that can be used for backup, restore, or testing purposes. BCV devices are required for SRDF/Star configurations to enable fast recovery in case of a disaster.The number of BCV devices must match the number of R1 devices in the SRDF/Star configuration.1
• Create an SRDF/Star composite group and options file. This step involves creating an SRDF/Star composite group on the control host using the symstar create command. An SRDF/Star composite group is a logical grouping of devices that span across three arrays and have different SRDF roles: R11, R21, and R22. An R11 device is an R1 device that is paired with another R1 device in a different SRDF group. An R21 device is an R2 device that is paired with another R1 device in a different SRDF group. An R22 device is an R2 device that is paired with another R2 device in a different SRDF group.The symstar create command also creates an options file that contains various parameters for the SRDF/Star configuration, such as RDF mode, RDF consistency, RDF emulation, and bias setting.1
• Perform the symstar setup operation and create composite groups on target sites. This step involves performing the symstar setup operation on the control host using the symstar setup command. This command establishes the SRDF/Star configuration by creating RDF pairs between devices in different arrays, creating RDF groups on each array, creating composite groups on each array, and synchronizing data across all devices.The symstar setup command also creates composite groups on the secondary and tertiary arrays using the same name and number as the composite group on the primary array.1

References:

• Dell EMC Solutions Enabler 9.2 SRDF Family CLI User Guide

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.

 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

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 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

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 kilometersand 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.

References:

• SRDF Star software uses and best practices
• SRDF/STAR
• Remote replication using SRDF

The SYMACL unique ID for a host system can be obtained in two ways: derived from a host-based passphrase or randomly generated by the Solutions Enabler lockbox file. The host-based passphrase is a string that the user can specify to generate a unique ID for the host. The passphrase can be entered interactively using the symacl -unique -passphrase command, or stored in a file and passed as an argument using the symacl -unique -passphrase -file command. The Solutions Enabler lockbox file is a secure file that stores encryption keys and other sensitive information. The lockbox file can also generate a random unique ID for the host using the symacl -unique command. The lockbox file must be created and initialized before using this method.

References:

• symacl -unique : Unable to obtain unique ID for host - Dell
• EMC – Symmetrix Access Control – symacl | SANSPIRE
• How to identify hostname and host ID for license generation

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

 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

In an SRDF/Star configuration, all SRDF/Star device pairs must be of the same geometry and size. This is because SRDF/Star uses concurrent SRDF to maintain synchronous and asynchronous SRDF sessions between three arrays. The devices in these sessions must have identical geometry to ensure data consistency56. References: Dell EMC Solutions Enabler 9.2 SRDF Family CLI User Guide, SRDF/Metro overview | Dell EMC PowerMax and VMAX All Flash: SRDF/Metro Overview and Best Practices

When the RDF-ECA timer expires, all RDF links will be in a ‘Suspend’ state. This is because the RDF-ECA timer is used to control how long SRDF waits for an acknowledgement from the remote array before it suspends the link. If an acknowledgement is not received within this time, SRDF assumes that there is a problem with the link or remote array and suspends the link to prevent data loss or corruption.

 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.

The data characteristics represent an Online Transaction Processing (OLTP) workload profile. OLTP workloads typically consist of a high percentage of small, random I/O operations2. In this case, 80% of the I/O is generated with 8 KB random small blocks, which is characteristic of OLTP workloads2. References: Use DISKSPD to test workload storage performance - Azure Stack HCI | Microsoft Learn

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.

When expanding the capacity of a three-brick PowerMax 8000 running PowerMaxOS 5978.444.444 configured with Flash Drives RAID 5 (7+1) with SCM drives, the minimum supported configuration is 1x RAID 5 (7+1) added to each brick. This ensures that each brick has additional capacity and maintains the balance of storage across all bricks2. References: Dell EMC PowerMax Family Product Guide PowerMaxOS, Dell PowerMax Family Site Planning Guide PowerMax 2000 and PowerMax 8000, POWERMAX FAMILY PowerMax 2000 and 8000 - Dell Technologies Partner Portal