Hi Nico,
Its unclear riak-admin status eventually calls riak_kv_stat:get_stats
which states
%%</dd><dt> mem_total
%%</dt><dd> The first element of the tuple returned by
%% {@link memsup:get_memory_data/0}.
%%
%%</dd><dt> mem_allocated
%%</dt><dd> The second element of the tuple returned by
%% {@link memsup:get_memory_data/0}.
%%
The man page for memsup states
Returns the result of the latest memory check, where Total is
the total memory size and Allocated the allocated memory size,
in bytes.
which doesn't tell me if that's filesystem cache or not. According to
top the riak beam.smp is using 3G of virtual and 2.7G of resident
on node1 which don't match any of the values from before. Attaching
to the riak node and running memory() I see
[{total,2392208240},
{processes,15012600},
{processes_used,12797856},
{system,2377195640},
{atom,824297},
{atom_used,812024},
{binary,898656},
{code,8336856},
{ets,556632}]
Which seems to reflect what top claims. I'm just curious what to look at
to determine when I need to add new nodes. I'm currently capturing the
statistics riak provides and putting them into rrds, and mean response time
is great (95,99, and 100 have spikes quite regularly which I still don't fully
understand the cause of, but mean/median is pretty good <1ms). But I'm
wondering when to detect if the whole thing will come crashing down.
I've used Cassandra for the last 20 months in production and had the same
issue, it works great then it falls over, and unfortunately with such evenly
space data, everything tends to fall over at once. I just don't want that
to happen with my riak cluster, so am wondering how to tell if you are close
to needing to grow.
Anyone have any ideas?
-Anthony
On Thu, Mar 24, 2011 at 01:21:05AM +0100, Nico Meyer wrote:
> 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(["[email protected]"]);
> >>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 [email protected]
> >>18729
> >>
> >>_______________________________________________
> >>riak-users mailing list
> >>[email protected]
> >>http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
> >
--
------------------------------------------------------------------------
Anthony Molinaro <[email protected]>
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