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From Brian Spindler <brian.spind...@gmail.com>
Subject Re: need to reclaim space with TWCS
Date Sat, 20 Jan 2018 15:49:02 GMT
Hi Alexander,  Thanks for your response!  I'll give it a shot.

On Sat, Jan 20, 2018 at 10:22 AM Alexander Dejanovski <
alex@thelastpickle.com> wrote:

> Hi Brian,
>
> You should definitely set unchecked_tombstone_compaction to true and set
> the interval to the default of 1 day. Use a tombstone_threshold of 0.6 for
> example and see how that works.
> Tombstones will get purged depending on your partitioning as their
> partition needs to be fully contained within a single sstable.
>
> Deleting the sstables by hand is theoretically possible but should be kept
> as a last resort option if you're running out of space.
>
> Cheers,
>
> Le sam. 20 janv. 2018 à 15:41, Brian Spindler <brian.spindler@gmail.com>
> a écrit :
>
>> I probably should have mentioned our setup: we’re on Cassandra version
>> 2.1.15.
>>
>>
>> On Sat, Jan 20, 2018 at 9:33 AM Brian Spindler <brian.spindler@gmail.com>
>> wrote:
>>
>>> Hi, I have several column families using TWCS and it’s great.
>>> Unfortunately we seem to have missed the great advice in Alex’s article
>>> here: http://thelastpickle.com/blog/2016/12/08/TWCS-part1.html about
>>> setting the appropriate aggressive tombstone settings and now we have lots
>>> of timestamp overlaps and disk space to reclaim.
>>>
>>>
>>>
>>> I am trying to figure the best way out of this. Lots of the SSTables
>>> with overlapping timestamps in newer SSTables have droppable tombstones at
>>> like 0.895143957 or something similar, very close to 0.90 where the full
>>> sstable will drop afaik.
>>>
>>>
>>>
>>> I’m thinking to do the following immediately:
>>>
>>>
>>>
>>> Set *unchecked_tombstone_compaction = true*
>>>
>>> Set* tombstone_compaction_interval == TTL + gc_grace_seconds*
>>>
>>> Set* dclocal_read_repair_chance = 0.0 (currently 0.1)*
>>>
>>>
>>>
>>> If I do this, can I expect TWCS/C* to reclaim the space from those
>>> SSTables with 0.89* droppable tombstones?   Or do I (can I?) manually
>>> delete these files and will c* just ignore the overlapping data and treat
>>> as tombstoned?
>>>
>>>
>>>
>>> What else should/could be done?
>>>
>>>
>>>
>>> Thank you in advance for your advice,
>>>
>>>
>>>
>>> *__________________________________________________*
>>>
>>> *Brian Spindler *
>>>
>>>
>>>
>>>
>>>
>> --
> -----------------
> Alexander Dejanovski
> France
> @alexanderdeja
>
> Consultant
> Apache Cassandra Consulting
> http://www.thelastpickle.com
>

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