any way to REALLY turn off commitlog?

[Keith Freeman <8f...@gmail.com>]

We're running an insert-heavy use-case and have set "durable_writes = 
false" for all of our keyspaces.  While inserts are coming in (about 
2000 1k-records per second), we are still seeing 50Mb written to files 
in the commitlog directory every 6-10 seconds (using iostat).

Anybody know why so much data would written in this situation? We're 
guessing that these writes are related to the system and system_traces 
keyspaces, right?  Is it considered ok to turn off durable_writes on 
those keyspaces?  (I couldn't find anything on this searching the 
message board or google).

(Note we have double- and triple- checked that all of our keyspaces 
definitely have durable_writes=false, with multiple clean-and-restarts 
of cassandra)

Re: any way to REALLY turn off commitlog?

[Benedict Elliott Smith <be...@datastax.com>]

Are you writing these records as batches (with begin batch, not begin
unlogged)? As a logged batch ('begin batch' is logged) gets written to a
system keyspace with CL before being applied to the underlying CF, and I'm
not sure we want to go special casing that for non-durable writes, since
you probably should just be using unlogged batches if you don't care.



On 27 March 2014 15:28, Keith Freeman <8f...@gmail.com> wrote:

> We're running an insert-heavy use-case and have set "durable_writes =
> false" for all of our keyspaces.  While inserts are coming in (about 2000
> 1k-records per second), we are still seeing 50Mb written to files in the
> commitlog directory every 6-10 seconds (using iostat).
>
> Anybody know why so much data would written in this situation? We're
> guessing that these writes are related to the system and system_traces
> keyspaces, right?  Is it considered ok to turn off durable_writes on those
> keyspaces?  (I couldn't find anything on this searching the message board
> or google).
>
> (Note we have double- and triple- checked that all of our keyspaces
> definitely have durable_writes=false, with multiple clean-and-restarts of
> cassandra)
>
>