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Creating a balanced storage configuration is important because SQL Server workloads can vary greatly and I/O patterns can often fluctuate due to changes in the database environment, evolving data-access patterns, or data growth. For most SQL Server workloads, it is recommended to configure the PowerVault ME5 array using the Virtual storage type and ADAPT as the RAID level.
For best performance, a minimum of 24 drives should be used when using the ADAPT RAID level because this is the minimum number required to create two Virtual storage pools, one per controller in a dual-controller system. Start with 24 SSD drives and add additional drives as needed to achieve performance and capacity requirements. A PowerVault ME5 array with SSDs spread evenly across 2 Virtual storage pools (one per controller) configured with the ADAPT RAID level provides the best overall balance of performance, flexibility, capacity, and data protection. Detailed information on ADAPT can be found in the PowerVault ADAPT Software paper.
There is a variety of other RAID levels and storage configurations available for very specific workloads. Make sure the design tradeoffs are completely understood when choosing custom configurations and settings. In many cases, modifying the storage configuration for existing volumes will involve halting I/O on those volumes, resulting in a SQL Server outage. For detailed information on all available choices, including ADAPT, see the PowerVault ME5 Administrator’s Guide.
The performance characteristics of the PowerVault ME5 largely depend on the RAID level chosen for the storage configuration. While the ADAPT RAID level provides the most balanced configuration, other RAID levels are available for maximum performance or maximum capacity. The two additional levels discussed in this section are RAID5 and RAID10. For all available RAID levels, consult the PowerVault ME5 Administrator’s Guide.
The performance numbers presented are maximum values on an PowerVault ME5 array with a minimum of 24 drives and two storage pools, one per controller. Note that performance among RAID levels only has significant variation in workloads such as OLTP where frequent writes occur. For read-only workloads such as OLAP, there is practically no performance benefit to select RAID levels based on performance. Use care when configuring multiple RAID levels on the same PowerVault ME5 array. Ensure that the number of drives in the storage pool is sufficient to provide the performance desired. Mixing RAID levels within a storage pool is not recommended. Remember that when selecting RAID levels, there are design considerations other than performance. RAID levels impact the data protection, capacity, and flexibility of the overall storage design. Therefore, the goal is to find the best balance of performance, data protection, capacity, and flexibility.
When using the ADAPT RAID level, the PowerVault ME5 can perform up to 170,000 IOPS using an OLTP workload[1] and up to 13 GB/sec for OLAP workloads[2].The solid OLTP performance and outstanding read performance, and the balance of performance, capacity, and data protection, make ADAPT a good choice for mixed-database workloads.
When additional performance and capacity is required, RAID5 can be used. In a RAID5 configuration, some disk resources that were reserved for data protection are used for additional capacity and performance. Therefore, RAID5 offers less data protection than ADAPT. However, it can deliver up to 207,000 IOPS for OLTP[3] workloads
For maximum OLTP performance, RAID10 can deliver up to 344,000 IOPS for OLTP3 workloads. In a RAID10 configuration, the usable capacity is reduced to 50% of raw capacity. Therefore, a RAID10 solution requires almost double the number of drives compared to more space-efficient RAID types.