IDA configuration parameter relationships
The following table shows the relationship that exists between IDA Width and Threshold, and the role they play in determining storage overhead and fault tolerance.
| Property | Defined by |
|---|---|
| Storage overhead | (IDA Width / Threshold) – 1.0 |
| Maximum fault tolerance | IDA Width – Threshold |
In summary, the ratio of IDA Width to IDA Threshold governs storage overhead. The closer the ratio is to 1.0, the lower the storage overhead. However, reducing this ratio reduces the gap between IDA Width and Threshold. The gap between them determines how many faults the system can tolerate, and directly feeds into the reliability and availability properties of the system. The only way for the gap to be significant, and for the ration to be small, is if both IDA Width and Threshold are large relative to their gap. Charts in the following sections illustrate this point.