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From aaron morton <>
Subject Re: memtable overhead
Date Tue, 23 Jul 2013 09:38:53 GMT
An empty memtable would not take up much space, a few KB I would assume.

However they are considered in the calculations that control how frequently to flush to disk.
The more CF's, even if they do not have data, the more frequently you will flush to disk.


Aaron Morton
Cassandra Consultant
New Zealand


On 23/07/2013, at 6:06 PM, MichaƂ Michalski <> wrote:

> Not sure how up-to-date this info is, but from some discussions that happened here long
time ago I remember that a minimum of 1MB per Memtable needs to be allocated.
> The other constraint here is memtable_total_space_in_mb setting in cassandra.yaml, which
you might wish to tune when having a lot of CFs.
> M.
> W dniu 23.07.2013 07:12, Darren Smythe pisze:
>> The way weve gone about our data models has resulted in lots of column
>> families and just looking for guidelines about how much space each column
>> table adds.
>> TIA
>> On Sun, Jul 21, 2013 at 11:19 PM, Darren Smythe <>wrote:
>>> Hi,
>>> How much overhead (in heap MB) does an empty memtable use? If I have many
>>> column families that aren't written to often, how much memory do these take
>>> up?
>>> TIA
>>> -- Darren

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