Clarifying withoutFetch() with LevelDB and

Daniel Iwan iwan.daniel at
Wed May 13 07:48:27 EDT 2015


I'm using 4 node Riak cluster v1.3.1

I wanted to know a little bit more about using withoutFetch() option when
used with levelDB.
I'm trying to write to a single key as fast as I can with n=3.
I deliberately create siblings by writing with stale vclock. I'm limiting
number of writes to 1000 per key to keep size of Riak object under control
and then I switch to another key. Siblings will probably never be resolved
(or resolved in realtime during sporadic reads)

Single write operation is about 250 bytes, rate 10-80 events per sec which
gives 3-20kB per second per node. So roughly 100kB / s for the cluster.

During the test I see activity on the on disk via iostat and it's between
20-30 MB/s on each node.
Even taking into account multiple copies and overhead of Riak (vclocks etc)
this seems to be pretty high rate.
I don't see any read activity which suggest withoutFetch() works as
After 2 mins of tests leveldb on each node is 250MB is size, before test

Am I using it incorrectly? 
Is writing in this way to a single key a good idea or will I be bitten by
How to explain high number of MB written to disks?


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