During the design phase of a StorageGRID implementation project covering three geo-distributed sites, a requirement...

A Global Server Load Balancer (GSLB) is the appropriate solution when StorageGRID client traffic must be intelligently directed among multiple geographically distributed sites. NetApp states that global load balancing integrates with DNS to provide intelligent routing across StorageGRID sites and can direct clients to the closest destination site, while also detecting site outages and redirecting requests to another available site. This global routing functionality is provided through a supported third-party load-balancing or DNS traffic-management solution.

A typical architecture combines GSLB at the global layer with site-local load balancers or StorageGRID Gateway Node HA groups. When an S3 client resolves the StorageGRID endpoint FQDN, the GSLB selects the appropriate site's virtual IP based on factors such as availability and network latency, thereby providing proximity-based client access.

Option B provides effective local site load balancing, but by itself does not choose the geographically closest site. Option A provides HA for interfaces within an HA group and is not a geographic traffic-management mechanism. Option C provides link-level redundancy and bandwidth aggregation rather than application-level site selection.

Therefore, D is the correct answer.

Reference topics: StorageGRID Load Balancing → Third-Party Load Balancers → Global Server Load Balancing (GSLB) → DNS-Based Site Selection → Geo-Distributed Client Access