Hi Anthony,
are you sure you are not including the filesystem cache in your
mem_allocated values? It will grow to use all of the free memory or the
total size of your bitcask data files, whichever is smaller.
We have about 100Mio keys per node, and riak uses about 7GB of RAM.
Cheers,
Nico
On 23.03.2011 23:24, Anthony Molinaro wrote:
So a question about when to add new nodes. I'm looking at the output of
this script and the output of riak-admin status to attempt to figure out
if it's time to grow a cluster.
I have 4 nodes 1024 partitions replication factor 3, currently with a
single bitcask single bucket where both the key and the value are 36 bytes.
According to the bitcask spreadsheet the overhead per key is 40 bytes
The current key counts/memory are
key_counts mem_total mem_allocated (key_count*76)
node1 22381785 25269010432 21015953408 1701015660
node2 22378092 25269010432 14076137472 1700734992
node3 22373770 25269010432 21565509632 1700406520
node4 22382394 25269010432 21493731328 1701061944
node2 failed at some point and was replaced with with a new node.
So there is some oddness here I don't understand. According to the
calculated value I should see about 1.7GB per box used, instead I see
21GB on most machines except for the one which was restarted which has
14GB. From looking at memory it seems like I should be adding some nodes
real soon or amount allocated will hit the total amount. Or maybe there's
a memory leak which will reduce the amount of memory (as with node2)?
I'm just trying to figure out why I seem to almost be out of memory with
23 million documents when the Bitcask capacity planning spreadsheet seems
to suggest I should be able to have 282 million with 20 GiB of free Ram.
Confused,
-Anthony
On Wed, Mar 16, 2011 at 12:04:48PM -0700, Aphyr wrote:
I'm trying to track some basic metrics so we can plan for cluster
capacity, monitor transfers, etc. Figured this might be of interest
to other riak admins. Apologies if my erlang is nonidiomatic, I'm
still learning. :)
#!/usr/bin/env escript
%%! -name riakstatuscheck -setcookie riak
main([]) -> main(["riak@127.0.0.1"]);
main([Node]) ->
io:format("~w\n", [
lists:foldl(
fun({_VNode, Count}, Sum) -> Sum + Count end,
0,
rpc:call(list_to_atom(Node), riak_kv_bitcask_backend, key_counts, [])
)
]).
$ ./riakstatus riak@127.0.0.1
18729
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