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When configuring Dell storage, consider the following business needs:
This section provides guidance and best practices for meeting such business needs.
A service-level objective (SLO) defines an expected average response-time target for a storage group. The following SLOs are available in the PowerMax storage array: the diamond SLO with defined, expected average response time targets, and the optimized SLO with no explicit response time target.
By default, the optimized SLO manages all the data in the PowerMax storage array. Because the PowerMax contains all NVMe flash devices, the optimized and the diamond settings are effectively the same. The actual response time of an application that is associated with each SLO varies based on the observed workload. Response time depends on average I/O size, read/write ratio, and the use of local or remote replication, along with the availability of other resources within the array. For more information, go to Dell Online Support and search for Dell FAST and PowerMax documentation.
Thin provisioning enables you to increase capacity utilization by presenting more storage to a host than is physically consumed and by allocating storage only as needed from a shared virtual pool. The storage allocation operations are performed in small units of storage (of one track or 128 KB) called virtually provisioned device extents.
Dell Technologies recommends the following best practices for creating thin LUNs to obtain optimal performance:
After creating the LUNs, create a server cluster for high availability and map the volumes to the server cluster by using auto provisioning. With auto provisioning:
At the time the masking view is created, a single operation automatically performs all required mapping and masking. This approach dramatically simplifies storage allocation.
Selecting the appropriate RAID type is an important decision for a successful implementation. Consider elements such as performance, capacity, and availability. Dell storage systems support RAID 5, and RAID 6.
Each RAID type provides different performance, capacity, and protection levels:
Customers select the RAID type and disk type combination based on their requirements. In a FAST for Virtual Pools (FAST VP) environment, Dell Technologies recommends RAID 5 for flash and RAID 6 for SATA. The following table shows how RAID levels compare in read, write, sequential read, and sequential write scenarios:
RAID level | Random read | Random write | Sequential read | Sequential write |
RAID 5 | Excellent | Good | Good | Moderate |
RAID 6 | Good | Poor | Good | Moderate |
Global memory is a crucial component in the solution architecture. All read and write operations are transferred to or from global memory. Transfers between the host processor and channel directors can be processed at much greater speeds than transfers involving physical drives. PowerMaxOS uses complex, intelligent, statistical pre-fetch algorithms, which can adjust to workload on the array by constantly monitoring, evaluating, and optimizing cache decisions.
Configuring multiple connections from the host servers (direct connect) or FC switch (SAN connect) to the system provides channel redundancy. With SAN connectivity through FC switches, each front-end port can support multiple host attachments, enabling storage consolidation across a large number of host platforms. The multiple connections are distributed across separate directors to ensure uninterrupted access in the event of a channel failure. A minimum of two connections per server or SAN provides full redundancy.
Host connectivity to the front-end director ports is spread across physical components for the most efficient form of redundancy.
Dell Technologies recommends the following best practices for connecting a host or cluster:
For cabling options, one approach is to connect all even-numbered ports to FabricA and all odd-numbered ports to FabricB.
Example: Port 4 and 24 on both directors 1 and 2
Example: Port 4 on directors 1, 2, 3, and 4.
The following figure shows an example of redundant SAN connectivity to a PowerMax array with a single node pair:
FC zoning partitions the FC fabric into multiple subsets. A zone includes FC initiators and targets and enables communication between them. Consider the following when setting the I/O paths:
PowerMax inline data reduction significantly increases the effective capacity of the PowerMax array by reducing the physical footprint of the dataset and, therefore, the number of NVMe flash disks required. Inline data reduction also intelligently optimizes system resources to ensure that the system is always delivering the best balance of performance and efficiency.
Data reduction is managed at the storage group level. You can easily enable or disable data reduction to target the workloads that would benefit most. You can also apply data reduction to existing data. Each storage group reports the effective data reduction ratio (CR) related to the data that is specific to that storage group. A PowerMax array typically consists of a variety of storage groups and SAP landscapes with production and nonproduction databases, each of which has its own achieved CR. The overall system CR is a mix of the various underlying storage group ratios. With a normal mix of SAP workloads, you can expect to see an approximately 2:1 system CR. This ratio could be higher or lower depending on the data mix. The Dell testing team observed a CR of 2.7:1 across the SAP landscape. When inline data reduction is combined with other PowerMax space-saving capabilities (such as Dell Virtual Provisioning technology, zero space reclaim, and space-efficient snapshots), an overall efficiency rate of 4:1 is achievable.
For more information, see the Dell PowerMax Data Reduction White Paper.
PowerMax File
Distributed SAP NetWeaver systems architecture requires that global file systems are physically shared from the ABAP SAP Central Services (ASCS) instance using the NFS protocol to all SAP NetWeaver Application Servers (AS) belonging to the same SAP system. For example:
Two methods are used to physically share these global file systems:
PowerMax File can provide storage-based NFS to satisfy the SAP global file system requirements.
Customers should plan, implement, and configure File in PowerMax storage arrays to obtain maximum operating efficiencies from the File component of the array. For more information, see theDell PowerMax File protocol guide.
Dell Technologies recommends the following best practices for SRDF/Metro configuration:
Note the following:
Dell Technologies recommends the following best practices for configuring your Data Domain system: