A SAN administrator is setting thresholds on trunks composed of four ISLs per trunk group. To allow for the loss of one ISL, which of the following values should be used for the bandwidth threshold of

A 50% threshold would be overly conservative, as it implies a total load of 2 units across 4 ISLs; if one fails, the 3 remaining ISLs would run at approximately 67% each, underutilizing the infrastructure.

If a trunk group has four ISLs and is designed to tolerate the loss of one ISL, the remaining three ISLs must be able to carry the entire load. Setting the bandwidth threshold for each ISL to 67% means that when this threshold is met, the total load across all four ISLs is 4 * 0.67 = 2.68 units. If one ISL fails, this 2.68 unit load is redistributed among the three remaining ISLs, resulting in each running at approximately 89.3% capacity (2.68 / 3), thus preventing overload and providing a reasonable operational buffer.

A 78% threshold would result in a total load of 3.12 units across 4 ISLs; if one ISL fails, the 3 remaining ISLs would have to handle 3.12 units, leading to an overload condition of 104% utilization per ISL.

A 90% threshold would lead to a total load of 3.6 units across 4 ISLs; if one ISL fails, the 3 remaining ISLs would be severely overloaded at 120% utilization each, making the system vulnerable.