Question:

How big should an orbserver ring buffer be?

Answer:

The ring buffer acts as a short term buffer for data. A reasonable rule of thumb would be to provide enough space for a few hours of data.

This should allow plenty of time for daily database cleanups to complete. During the database cleanup (using rtdbclean(1)), the processes which write to the database -- like orb2db(1) and orb2dbt(1) -- stop, restarting only when the cleanup is complete. If data were to fall off the orb in the meantime, it would be lost.

There is a hard limit of 2 Gbytes on ring buffer size (on a 32 bit system), but other limits like real memory usually impose a lower limit. Having a really large ring buffer can be a problem when some program searches through the ring buffer from the beginning, causing lots of paging on the machine.