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From Paolo Crosato <>
Subject RE: hardware sizing for cassandra
Date Tue, 09 Sep 2014 19:52:42 GMT
Every node should have at least 4 cores, with a maximum of 8. Memory shouldn't be higher than
32g, 16gb is good for a start. Every node should be a phisical machine, not a virtual one,
or at least a virtual machine with an ssd hd subsystem. The disk subsystem should be directly
connected to the machine, no sans or fiber channel between. Cassandra is cpu and io bounded,
so you should get the maximum io speed and a reasonable number of cores.

Number of nodes should be 3 at least with replication factor of 2. You should prefer more
less powerful nodes then fewer more powerful nodes.

Disk size depends on your workload, although you should always keep 50% of the disk free in
the case repair sessions requires space, or perform sub range repairs.

In my experience a 1GB link between nodes is ok, but the less lag the better.

Summing up if you need to save some money, get 4 cores and 16 gb or ram, 32 is rarely needed
and 64 a waste. 8 cores would probably be too much with 1000 writes a second.


Paolo Crosato
Software engineer/Custom Solutions

Da: Chris Lohfink <>
Inviato: martedì 9 settembre 2014 21.26
Oggetto: Re: hardware sizing for cassandra

It depends.  Ultimately your load is low enough a single node can probably handle it so you
kinda want a "minimum" cluster.  Different people have different thoughts on what this means
- I would recommend 5-6 nodes with a 3 replication factor.  (say m1.xlarge, or c3.2xlarge
striped ephemerals, I like i2's but kinda overkill here).  Nodes with less then 16gb of ram
wont last long so should really start around there.


On Sep 9, 2014, at 11:02 AM, Oleg Ruchovets <> wrote:

> Hi ,
>    Where can I find the document with best practices about sizing for cassandra deployment?
>    We have 1000 writes / reads per second. record size 1k.
> Questions:
>    1) how many machines do we need?
>    2) how many ram ,disc size / type?
>    3) What should be network?
> I understand that hardware is very depends on data distribution and access pattern and
other criteria, but I still want to believe that there is a best practice :-)
> Thanks
> Oleg.

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