I have a few noob questions regarding system projections and disk space implications of using these.
- We are doing some capacity planning for a new event sourced system.
- We’ve estimated we’ll have an events growth rate of n GB/mth.
- We have one system projection (by_category) enabled and it seems the default for this is that emit is enabled.
- All our events are named so they are picked up by this system projection (ie every event has a category).
If the system projection is emitting events, will this double our actual disk usage? (ie two copies on disk of every event)
Should we now be planning for 2n GB/mth disk space growth?
Followup questions (for better understanding)
- Is it possible to change the system projection to not emit but rather link events?
- Does it even make sense to make system projections link rather than emit?
- Why/when would we not want to always link events in projections rather than emit?
- If we enabled a second system projection (eg by_type) would we then see 3n GB/mth disk space growth?
I’m happy to read docs if this is all explained somewhere.