Choosing a RAID level for a particular machine workload relies on the consideration of a lot of different factors if you want your machine/machines to run at their maximum potential and with Best Practices in mind

Other factors

• Manufacturers Disk IOPs values

• Type of Disk. E.g SATA, SAS, NSATA, SSD and FC

• Speed of Disk. E.g 15K or 10K RPM etc

• To ensure a stable and consistent I/O response, maximize the number of VM storage disks available. This strategy enables you to spread disk reads and writes across multiple disks at once, which reduces the strain on a smaller number of drives and allows for greater throughput and response times.

• Controller and transport speeds affect VM performance

• Disk Cost.

• Some vendors have their own proprietary RAID Level. E.g Netapp RAID DP

• The RAID level you choose for your LUN configuration can further optimize VM performance. But there’s a cost-vs-functionality component to consider. RAID 0+1 and 1+0 will give you the best virtual machine performance but will come at a higher cost, because they utilize only  50% of all allocated disks

• RAID 5 will give you more storage for your money, but it requires you to write parity bits across drives. However slower SANs or local VM storage can create a resource deficit which can create bottlenecks

• Cache Sizes

• Connectivity. E.g. ISCSI, FC or FCOE. Fibre Channel and iSCSI are the most common transports and within these transports, there are different speeds. E.g. 1/10 GB iSCSI and 4/8 GB FC

• Thin provisioning. This will take up less space on the SAN but create extra I/O utilisation due to the zeroing of blocks on write

• De-deuplication. This does not necessarily improve storage performance but it stops duplicate data on storage which can save a great deal of money

• Predictive Scheme. Create several LUNs with varying storage characteristics

• Adaptive Scheme. Create large datastores and place VMs on and monitor performance

Please see the following links for general information on RAID and IOPS

http://www.electricmonk.org.uk/2013/01/03/raid-levels/

http://www.electricmonk.org.uk/2012/01/30/iops/