Seems like this is getting asked more and more, that’s unfortunate. Wish I had 
time to fix this by making flush smarter or TWCS split old data. But I don’t. 

You can search the list archives for more examples, but what’s probably 
happening is that you have sstables overlapping which prevents TWCS from 
dropping them when fully expired

The overlaps probably come from either probabilistic read repair or speculative 
retry read-repairing data into the memtable on the dc that coordinates your 
reads

Cassandra-13418 (  https://issues.apache.org/jira/browse/CASSANDRA-13418 ) 
makes it so you can force sstables to be dropped at expiration regardless of 
overlaps, but you have to set some properties because it’s technically unsafe 
(if you write to the table with anything other than ttls).



-- 
Jeff Jirsa


> On Dec 24, 2018, at 12:05 AM, Eunsu Kim <eunsu.bil...@gmail.com> wrote:
> 
> I’m using TimeWindowCompactionStrategy.
> 
> All consistency level is ONE.
> 
>> On 24 Dec 2018, at 2:01 PM, Jeff Jirsa <jji...@gmail.com> wrote:
>> 
>> What compaction strategy are you using ?
>> 
>> What consistency level do you use on writes? Reads? 
>> 
>> -- 
>> Jeff Jirsa
>> 
>> 
>>> On Dec 23, 2018, at 11:53 PM, Eunsu Kim <eunsu.bil...@gmail.com> wrote:
>>> 
>>> Merry Christmas
>>> 
>>> The Cassandra cluster I operate consists of two datacenters.
>>> 
>>> Most data has a TTL of 14 days and stores one data for each data center. 
>>> (NetworkTopologyStrategy, datacenter1: 1, datacenter2: 1)
>>> 
>>> However, for a few days ago, only the datacenter1 disk usage is increasing 
>>> rapidly.
>>> 
>>> There is no change in nodetool cleanup on each node of datacenter1.
>>> 
>>> How does this happen? What can I do?
>>> 
>>> I would appreciate your advice.
>>> 
>>> Thank you in advance.
>>> 
>>> <PastedGraphic-2.png>
>>> 
>>> <PastedGraphic-1.png>
>> 
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