User guide
Technical white paper | HP Enterprise Virtual Array Storage and VMware vSphere 4.x and 5.x configuration best practices
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You can use Command View EVA to set a disk drive failure protection level in the properties for the particular disk group, as
shown in Figure 6.
Figure 6. Disk protection level as seen in Command View EVA
Note
Vraid0 Vdisks are not protected.
For a disk group where the largest disk drive capacity is 146 GB and double disk drive failure protection is required, sparing
capacity can be calculated as follows:
Sparing does not span disk groups; each disk group must be allocated its own sparing space based on the above formula.
Application-specific considerations
One of the most common misconceptions about server virtualization is that when an application is virtualized, its storage
requirement can be reduced or changed. In practice, due to the aggregation of resources, virtualization typically increases
the storage requirement. Thus, when you virtualize an application, you should maintain the storage required by this
application while also provisioning additional storage for the virtual infrastructure running the application.
Sizing storage for any application that is being virtualized begins with understanding the characteristics of the workload. The
following formula is used to calculate the spindle count required for a random access workload:
In this formula, the Total IOPS value and read/write ratio are application-dependent.
The RAID penalty value is defined as the number of I/Os to disk that result from a guest I/O due to the particular Vraid level
being used. For example, every I/O request to a Vraid1 Vdisk results in two I/Os being issued in the array in order to provide
data protection.
Best practice for sizing an EVA disk group
• When sizing an EVA disk group, start by determining the characteristics of the application’s workload, which will help you
optimize array performance.
Storage optimization requirements
In addition to the number of disks required to handle the performance characteristics of the particular application, you must
also account for the total storage capacity required by the applications and VMs being deployed.
This storage capacity can be determined by simple arithmetic by adding the storage requirements for each VM to the
capacity required for the various applications. However, depending on your particular storage optimization objective, the
actual formatted capacity yielded can be lower than the simple aggregation of the required number of EVA drives.