On Fri, Jun 5, 2015 at 10:30 AM, Kévin LOVATO <klov...@alprema.com> wrote:
> > I have a column family with data (metrics) that is never overwritten and > only deleted using TTLs, and I am wondering if it would be reasonable to > have a very low gc_grace_period (even 0) on that CF. I would like to do > that mainly to save space and also to prevent tombstone scanning. > Yes, you can safely lower gc_grace_seconds. You would only _not_ want to lower gc_grace_seconds if you did deletes or overwrote cells with a lower TTL. > > From what I understand of what I could read online, when an expired TTLed > column is compacted, it is replaced by a tombstone, so having > gc_grace_period would prevent that. Although this would allow the > appearance of ghost/zombie columns. > > The question I'm trying to answer here is the following: Would those ghost > columns be able to appear, and if so, would it be a problem, since they > would themselves be marked as "expired"? > You don't need to worry about expired data being revived because every node that has a copy of that data will have the same TTL. -- Tyler Hobbs DataStax <http://datastax.com/>
