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From Alain RODRIGUEZ <arodr...@gmail.com>
Subject Re: Cassandra 2.1.12 Node size
Date Thu, 14 Apr 2016 14:14:34 GMT
>
> Would adding nodes be the right way to start if I want to get the data per
> node down


Yes, if everything else is fine, the last and always available option to
reduce the disk size per node is to add new nodes. Sometimes it is the
first option considered as it is relatively quick and quite strait forward.

Again, 50 % of free disk space is not a hard limit. To give you a rough
idea, if the biggest sstable is 100 GB big and you still have 400 GB free,
you will probably be good to go, excepted if 4 compaction of 100 GB trigger
at the same time, filling up the disk.

Now is the good time to think of a plan to handle the growth for you, but
don't worry if data reaches 60%, it will probably not be a big deal.

You can make sure that:

- There are no snapshots, heap dumps or data not related with C* taking
some space
- The biggest sstables tombstone ratio are not too high (are tombstones are
correctly evicted ?)
- You are using compression (if you want too)

Consider:

- Adding TTLs to data you don't want to keep forever, shorten TTLs as much
as allowed.
- Migrating to C*3.0+ and take advantage of the new engine storage

C*heers,
-----------------------
Alain Rodriguez - alain@thelastpickle.com
France

The Last Pickle - Apache Cassandra Consulting
http://www.thelastpickle.com


2016-04-14 15:41 GMT+02:00 Aiman Parvaiz <aiman@flipagram.com>:

> Thanks for the response Alain. I am using STCS and would like to take some
> action as we would be hitting 50% disk space pretty soon. Would adding
> nodes be the right way to start if I want to get the data per node down
> otherwise can you or someone on the list please suggest the right way to go
> about it.
>
> Thanks
>
> Sent from my iPhone
>
> On Apr 14, 2016, at 5:17 PM, Alain RODRIGUEZ <arodrime@gmail.com> wrote:
>
> Hi,
>
> I seek advice in data size per node. Each of my node has close to 1 TB of
>> data. I am not seeing any issues as of now but wanted to run it by you guys
>> if this data size is pushing the limits in any manner and if I should be
>> working on reducing data size per node.
>
>
> There is no real limit to the data size other than 50% of the machine disk
> space using STCS and 80 % if you are using LCS. Those are 'soft' limits as
> it will depend on your biggest sstables size and the number of concurrent
> compactions mainly, but to stay away from trouble, it is better to keep
> things under control, below the limits mentioned above.
>
> I will me migrating to incremental repairs shortly and full repair as of
>> now takes 20 hr/node. I am not seeing any issues with the nodes for now.
>>
>
> As you noticed, you need to keep in mind that the larger the dataset is,
> the longer operations will take. Repairs but also bootstrap or replace a
> node, remove a node, any operation that require to stream data or read it.
> Repair time can be mitigated by using incremental repairs indeed.
>
> I am running a 9 node C* 2.1.12 cluster.
>>
>
> It should be quite safe to give incremental repair a try as many bugs have
> been fixe in this version:
>
> FIX 2.1.12 - A lot of sstables using range repairs due to anticompaction
> - incremental only
>
> https://issues.apache.org/jira/browse/CASSANDRA-10422
>
> FIX 2.1.12 - repair hang when replica is down - incremental only
>
> https://issues.apache.org/jira/browse/CASSANDRA-10288
>
> If you are using DTCS be aware of
> https://issues.apache.org/jira/browse/CASSANDRA-11113
>
> If using LCS, watch closely sstable and compactions pending counts.
>
> As a general comment, I would say that Cassandra has evolved to be able to
> handle huge datasets (memory structures off-heap + increase of heap size
> using G1GC, JBOD, vnodes, ...). Today Cassandra works just fine with big
> dataset. I have seen clusters with 4+ TB nodes and other using a few GB per
> node. It all depends on your requirements and your machines spec. If fast
> operations are absolutely necessary, keep it small. If you want to use the
> entire disk space (50/80% of total disk space max), go ahead as long as
> other resources are fine (CPU, memory, disk throughput, ...).
>
> C*heers,
>
> -----------------------
> Alain Rodriguez - alain@thelastpickle.com
> France
>
> The Last Pickle - Apache Cassandra Consulting
> http://www.thelastpickle.com
>
> 2016-04-14 10:57 GMT+02:00 Aiman Parvaiz <aiman@flipagram.com>:
>
>> Hi all,
>> I am running a 9 node C* 2.1.12 cluster. I seek advice in data size per
>> node. Each of my node has close to 1 TB of data. I am not seeing any issues
>> as of now but wanted to run it by you guys if this data size is pushing the
>> limits in any manner and if I should be working on reducing data size per
>> node. I will me migrating to incremental repairs shortly and full repair as
>> of now takes 20 hr/node. I am not seeing any issues with the nodes for now.
>>
>> Thanks
>>
>>
>>
>>
>

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