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From Jeff Jirsa <>
Subject Re: TWCS and gc_grace_seconds
Date Fri, 18 Oct 2019 06:05:49 GMT
Is everything in the table TTL’d? 

Do you do explicit deletes before the data is expected to expire ? 

Generally speaking, gcgs exists to prevent data resurrection. But ttl’d data can’t be
resurrected once it expires, so gcgs has no purpose unless you’re deleting it before the
ttl expires. If you’re doing that, twcs won’t be able to drop whole sstables anyway, so
maybe LCS will be less disk usage (but much higher IO)

> On Oct 17, 2019, at 10:36 PM, Adarsh Kumar <> wrote:
> Hi,
> We have a use case of time series data with TTL where we want to use TimeWindowCompactionStrategy
because of its better management for TTL and tombstones. In this case, data we have is frequently
deleted so we want to reduce gc_grace_seconds to reduce the tombstones' life and reduce pressure
on storage. I have following questions:
> Do we always need to run repair for the table in reduced gc_grace_seconds or there is
any other way to manage repairs in this vase
> Do we have any other strategy (or combination of strategies) to manage frequently deleted
time-series data
> Thanks in advance.
> Adarsh Kumar

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