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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HP defines three storage optimization schemes, each of which is subject to specific storage overhead and deployment
considerations:
• Cost
• Availability
• Performance
Optimizing for cost
When optimizing for cost, you goal is to minimize the cost per GB (or MB). Thus, it makes sense to minimize the number of
disk groups; in addition, since the cost per GB is lower as drive capacity increases, it is best to use the largest disks of the
same capacity within a particular disk group.
Even if you have disks with different capacities, it is better to use them in a single disk group rather than creating multiple
disk groups.
Best practice for filling the EVA array
• To optimize performance, fill the EVA with as many disks as possible using the largest, equal-capacity disks. Note that the
use a few larger drives with many small drives is inefficient due to sparing considerations.
Optimizing for availability
When optimizing for availability, your goal is to accommodate particular levels of failures in the array.
Availability within the array – and its usable capacity – can be impacted by a range of factors, including:
• Disk group type (enhanced or basic)
• Vdisk Vraid type
• Number and variety of disks in the disk group
• Protection levels
• Use of array-based copies
Typically, the additional protection provided by using double disk drive failure protection at the disk group-level cannot be
justified given the capacity implications; indeed, single disk drive failure protection is generally adequate for most
environments.
Enhanced disk groups offer features such as:
• Vraid6 protection, along with the traditional EVA Vraid0, 1, and 5
• Additional metadata protection, which is associated with a further storage capacity overhead
Many database applications use Vraid1 for database log files to guarantee performance and availability. However, while
providing stronger data protection than Vraid5, Vraid1 has a much higher storage cost.
Best practice for protecting the disk group
• Single disk drive protection is sufficient for a disk group unless the mean time to repair (MTTR) is longer than seven days.
Best practices for using Vraid
• Only use Vraid6 when it is a requirement for your deployment.
• Vraid5 comes at a lower storage-capacity cost and provides adequate redundancy for most ESX deployments.
Optimizing for performance
When optimizing for performance, your goal is to drive as much performance as possible from the system.
However, configuring for optimal performance may have an impact on usable storage capacity. For example, it may be
desirable to segregate small random workloads with short response time requirements from sequential workloads. In this
use case, you should create two disk groups, even though this configuration would create additional sparing capacity
utilization and reserved sparing capacity within each disk group.
Best practice for using disks of various performance characteristics
• When using disks of varying performance characteristics, use a single disk group rather than multiple disk groups.
Summary
• The use of a single EVA disk group is typically adequate for all storage optimization types (cost, performance, capacity).