Well, apparently, Catalyst was the central database. But again - we don't really have any information whatsoever about this process of harvesting. Like... there is literally no information - at least none that I can find. It's like they just say it happens, and then it's just left for us to accept it without question.
Also... isn't harvesting the way we're made to understand it just another way of saying "synthesis"... without the mass destruction?
Again.
Read the codex.
http://masseffect.wi...com/wiki/Reaper
http://masseffect.wi...dex/The_Reapers
Harvesting
Even with all the Reapers' power, harvesting every sapient species in an entire galaxy can take decades or even centuries. The most time-consuming part of the process is gathering DNA from the population. To accelerate the effort, the Reapers follow a consistent procedure.
Victims who cooperate, surrender, or are captured by husks are sorted into camps. It is believed the husks possess receptors that allow them to analyze a victim's DNA through sight, smell, or touch. Victims that meet their standards are herded from the camps into processor ships. Those the husks deem insufficient are either turned into husks themselves or indoctrinated to serve as slave labor. The Reapers use this last option to give their victims false hope -- many captives who would otherwise fight back become docile when they see members of their own kind obey and survive.
The processor ships reduce victims to a transportable liquid. Like in a slaughterhouse, the ships' design prevents victims from seeing or hearing what happens elsewhere so that they do not panic. The victims are ushered into locking pods, then rent apart and dissolved into paste that is flushed to storage vats.
The rate of killing is phenomenal. Intelligence estimates suggest there are more than 400 processor ships on Earth, killing approximately 1.86 million humans per day. In combination with battlefield deaths, disease, and famine, this pace will result in the complete depopulation of Earth within a decade. As the husks and indoctrinated slaves build more slaughtering facilities, the kill rate can only increase.
And before you say this is an external source: these are direct copies of the Codex in the game.
And to be complete:
The Citadel races have classified the known variants of Reapers into four types:
* CAPITAL SHIPS are Sovereign-class Reapers two kilometers in length. They typically target the dreadnoughts, defense installations, and industrial cities of organic civilizations. Experts believe the Reapers harvest a single species of organics during each cycle of extinction to create these massive ships. Some capital ships are capable of launching small drones equivalent to fighters.
* DESTROYERS are 160 meters long and, in astounding numbers, make up the bulk of the Reaper fleet. They engage cruisers and other, smaller ships, as well as communications posts and enemy command centers. Research suggests destroyers are created from those species that are not harvested to make capital ships.
* TROOP TRANSPORTS carry husks to unconquered planets and bring victims of the harvest to Reaper processing centers. They vary in length from 200 meters to one kilometer, but, unlike capital ships and destroyers, do not appear to be self-aware. Instead, other Reapers operate troop transports remotely.
* PROCESSORS, also called "slaughter ships," are mobile centers for mass DNA harvesting. Like troop transports, processors appear to be remotely operated by sapient Reapers.