Explanation
To satisfy the customer's needs for high-performance, low-latency applications at edge locations, the best deployment option is to use a new three-node vSAN 8.0 All-Flash Cluster with OSA in each edge location and configure each application VM with a RAID-1 VM storage policy. This option will provide the following benefits:
All-flash clusters offer the highest performance and lowest latency for vSAN, as they use flash devices for both cache and capacity tiers. Flash devices have faster read and write operations than magnetic disks, and they also support advanced features such as deduplication, compression, and encryption.
OSA stands for One Socket Architecture, which means that each host has only one CPU socket with multiple cores. This reduces the licensing cost and complexity of vSphere and vSAN, as well as the power consumption and cooling requirements of the hosts. OSA also improves the performance of vSAN by eliminating the NUMA effect, which is the latency caused by accessing memory or devices across different CPU sockets.
RAID-1 is a mirroring technique that creates two copies of each data component and places them on different hosts. This provides high availability and fault tolerance for the application VMs, as they can survive the failure of one host or disk. RAID-1 also offers better performance than RAID-5 or RAID-6, as it does not incur any parity overhead or additional write operations.
The other options are not optimal for the customer's needs, as they either sacrifice performance or capacity.
Option A uses RAID-5, which is an erasure coding technique that splits each data component into three data segments and one parity segment, and distributes them across four hosts. This reduces the capacity consumption by 25%, but it also increases the write latency and network traffic, as each write operation requires four hosts to participate. Option C uses ESA, which stands for Enterprise Storage Architecture, which means that each host has two CPU sockets with multiple cores. This increases the licensing cost and complexity of vSphere and vSAN, as well as the power consumption and cooling requirements of the hosts.
ESA also introduces the NUMA effect, which can degrade the performance of vSAN by adding latency to access memory or devices across different CPU sockets. Option D uses RAID-5 with ESA, which combines the disadvantages of both options A and C.