Assuming 40 pairs, 2 ticks per second and 1kb to store a tick (including timestamps, indexes etc), I reckon that's about 70TB for 40 years worth of data, not counting weekends.
I've assumed only outright ticks, hence the 40 pairs - in reality most banks store the crosses as well, which can be up to 1,600 pairs (40 x 40), which will get you into the PB range for the 40 years.
I've assumed only outright ticks, hence the 40 pairs - in reality most banks store the crosses as well, which can be up to 1,600 pairs (40 x 40), which will get you into the PB range for the 40 years.