Hi,
I have a few questions about Riak memory usage.
We're using Riak 1.3.1 on a 3 node cluster. According to bitcask capacity
calculator (
http://docs.basho.com/riak/1.3.1/references/appendices/Bitcask-Capacity-Planning/)
Riak should use about 30Gb of RAM for out data. Actually, it uses about
45Gb and I can't figure out why. I'm looking at %MEM column in top on each
node for a beam.smp process.
We have:
* about 235,000,000 keys
* one bucket with 1-byte name
* average key size about 24 bytes
* n_val = 2
Bucket properties:
{"props":{"allow_mult":false,"basic_quorum":false,"big_vclock":50,"chash_keyfun":{"mod":"riak_core_util","fun":"chash_std_keyfun"},"dw":"quorum","last_write_wins":false,"linkfun":{"mod":"riak_kv_wm_link_walker","fun":"mapreduce_linkfun"},"n_val":2,"name":"c","notfound_ok":true,"old_vclock":86400,"postcommit":[],"pr":0,"precommit":[],"pw":0,"r":"one","rw":"quorum","small_vclock":50,"w":"one","young_vclock":20}}
Disk usage is also about 1,5 times more than I have expected (270Gb instead
of 180Gb). I rechecked that I have n_val=2 (not 3), it seems alright. Why
this could happen?
Second question is about performance degradation when Riak uses almost all
available memory on the node. We see that 95/99 put percentiles twice as
large for nodes which don't have much free RAM. How much free memory I
should have to keep performance high?
And the last question about memory_total metric. riak-admin status returns
value which is less than actual memory consumption as seen in the top.
According to memory_total description (
http://docs.basho.com/riak/1.3.1/references/appendices/Inspecting-a-Node/)
they should be equal. Why they are not?
Alexander
_______________________________________________
riak-users mailing list
riak-users@lists.basho.com
http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
