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From aaron morton <aa...@thelastpickle.com>
Subject Re: Tuning cassandra (compactions overall)
Date Wed, 16 May 2012 09:45:00 GMT
> 1 - I got this kind of message quite often (let's say every 30 seconds) :
You are running out of memory. Depending on the size of your schema and the work load you
will want to start with 4 or 8 GB machines. But most people get the best results with 16Gb.

On AWS the common setup is to use m1.xlarge.

 2 - I shared 2 screenshot the cluster performance (via OpsCenter) and
> 
> the hardware metrics (via AWS).

The other system resources and throughput will be affected if cassandra does not have enough
memory to work with. 

There are some changes you can make to mitigate things (let me know if you need help), but
this is essentially a memory problem. 

Cheers

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 16/05/2012, at 4:31 AM, Alain RODRIGUEZ wrote:

> Hi,
> 
> I'm using a 2 node cluster in production ( 2 EC2 c1.medium, CL.ONE, RF
> = 2, using RP)
> 
> 1 - I got this kind of message quite often (let's say every 30 seconds) :
> 
> WARN [ScheduledTasks:1] 2012-05-15 15:44:53,083 GCInspector.java (line
> 145) Heap is 0.8081418550931491 full.  You may need to reduce memtable
> and/or cache sizes.  Cassandra will now flush up to the two largest
> memtables to free up memory.  Adjust flush_largest_memtables_at
> threshold in cassandra.yaml if you don't want Cassandra to do this
> automatically
> WARN [ScheduledTasks:1] 2012-05-15 15:44:53,084 StorageService.java
> (line 2645) Flushing CFS(Keyspace='xxx', ColumnFamily='yyy') to
> relieve memory pressure
> 
> Is that a problem ?
> 
> 2 - I shared 2 screenshot the cluster performance (via OpsCenter) and
> the hardware metrics (via AWS).
> 
> http://img337.imageshack.us/img337/6812/performance.png
> http://img256.imageshack.us/img256/9644/aws.png
> 
> What do you think of these metrics ? Are frequents compaction normal ?
> What about having a 60-70% cpu load for 600 Reads&Writes/sec with this
> hardware ? Is there a way to optimize my cluster ?
> 
> Here you got the main points of my cassandra.yaml :
> 
> flush_largest_memtables_at: 0.75
> reduce_cache_sizes_at: 0.85
> reduce_cache_capacity_to: 0.6
> concurrent_reads: 32
> concurrent_writes: 32
> commitlog_total_space_in_mb: 4096
> rpc_server_type: sync (I am going to switch to hsha, because we are
> using ubuntu)
> #concurrent_compactors: 1 (commented, so I use default)
> multithreaded_compaction: false
> compaction_throughput_mb_per_sec: 16
> rpc_timeout_in_ms: 10000
> 
> others tuning options (as many of the ones above) are default.
> 
> Any advice or comment would be appreciated :).
> 
> Alain


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