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From DuyHai Doan <doanduy...@gmail.com>
Subject Re: Max number of windows when using TWCS
Date Mon, 11 Feb 2019 20:23:41 GMT
No worry for overlapping, the use-case is about events/timeseries and there
is almost no delay so it should be fine.

On the note-side, since we have the guarantee to have 1 SSTable/day of
ingestion, this is very easy to "emulate" incremental backup. You just need
to find the generated SSTable with the latest create date and back it up
every day at midnight with a script.

Purging data is also straightforward, just dropping SSTables (by a script)
where create date is older than a threshold, we don't even need to rely on
TTL



On Mon, Feb 11, 2019 at 9:19 PM Jeff Jirsa <jjirsa@gmail.com> wrote:

> Wild ass guess based on a large use case I knew about at the time
>
> If you go above that, I expect it’d largely be fine as long as you were
> sure they weren’t overlapping so reads only ever touched a small subset of
> the windows (ideally 1).
>
> If you have one day windows and every read touches all of the windows,
> you’re going to have a bad time.
>
> --
> Jeff Jirsa
>
>
> On Feb 11, 2019, at 12:12 PM, DuyHai Doan <doanduyhai@gmail.com> wrote:
>
> Hello users
>
> On the official documentation for TWCS (
> http://cassandra.apache.org/doc/latest/operating/compaction.html#time-window-compactionstrategy)
> it is advised to select the windows unit and size so that the total number
> of windows intervals is around 20-30.
>
> Is there any explanation for this range of 20-30 ? What if we exceed this
> range, let's say having 1 day windows and keeping data for 1year, thus
> having indeed 356 intervals ? What can go wrong with this ?
>
> Regards
>
> Duy Hai DOAN
>
>

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