This is all from memory, so treat with caution. The S in SATA is serial. The older IDE jobs are PATA - parallel. Two PATA drive share the available bandwidth

This is all from memory, so treat with caution. The S in SATA is serial. The older IDE jobs are PATA - parallel. Two PATA drive share the available bandwidth (for want of a better word) and multiple SATAs have all the bandwidth available simultaneously to each device. Copying from one PATA disk to another on the same bus is horrible - in out, in out shake it all about at a few 10s of MBs-1. Copying from one SATA to another runs at full speed. For real speed you need SSD and hardware RAID with whopping caches and a price to match. For huge storage, reliability and a fairly eye watering price, why not use SSD to cache fast SAS 2.5" spinning rust with a decent hardware RAID. Oh I've just started to specify a SAN/NAS!