EMC Certification DEE-1111 Passing Score

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

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

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 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