Hi thanks for the quick reply!
Does this mean that VeloSSD needs 16GB for each TB of HDD, or is it user-definable? My example was made-up, but I agree it would not be good to max out the SSD carrying the OS.
If one was thinking of buying an SSD for the first time, it would be interesting to know what the minimum requirements for VeloSSD cache space per TB are, so that value-for-money could be better assessed. Some of the smaller SSDs are getting cheap eg 60GB OCZ Agility 3 for around 55 GBP.