EMC Updated DEE-1111 Exam Questions and Answers by richard

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.

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

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) array1. It supports pre-sync data between arrays and then schedule downtime to do the cutover1. References: Dell EMC PowerMax and VMAX: Non-Disruptive Migration Best Practices and Operational Guide

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