1. It won't make a load take 12 hours unless we're talking a load that is in total, similar to the size of the disk. A slow, newer SATA drive will read and write at at ~50MB/sec at minimum, so the whole 320GB can be scanned at 3GB per minute. Thats ~ 5 hours. It is not likely that 20M records is over 20GB, and at that size there is no way the disk is the bottleneck.
