Re: Evict Tombstones with STCS

[Alain RODRIGUEZ <ar...@gmail.com>]

Hi, I think you got it, this is probably the way to go:


> And if it so, forceUserdefinedcompaction or setting unchecked_tombstone_compactions
> to true wont help either as tombstones are less than 20% and not much disk
> would be recovered.


But if you have less than 20% tombstones in there I am not sure that
compacting those tables will help anyhow. It's probably time to add
capacity (nodes, as you can't add disks).

If you still want to give it a try, set the unchecked_tombstone_compactions
to true and the ratio to10% and see how it goes.

An other option to have better control on disk size and being able to use
up to 70% - 80% of the disk, then LCS might be a good option, if it fits
with your use case.

C*heers,

-----------------------
Alain Rodriguez - alain@thelastpickle.com
France

The Last Pickle - Apache Cassandra Consulting
http://www.thelastpickle.com

2016-05-28 20:24 GMT+01:00 Anuj Wadehra <an...@yahoo.co.in>:

> Hi,
>
> We are using C* 2.0.x . What options are available if disk space is too
> full to do compaction on huge sstables formed by STCS (created around long
> ago but not getting compacted due to min_compaction_threshold being 4).
>
> We suspect that huge space will be released when 2 largest sstables get
> compacted together such that tombstone eviction is possible. But there is
> not enough space for compacting them together assuming that compaction
> would need at least free disk=size of sstable1 + size of sstable 2 ??
>
> I read STCS code and if no sstables are available for compactions, it
> should pick individual sstable for compaction. But somehow, huge sstables
> are not participating in individual compaction.. is it due to default 20%
> tombstone threshold?? And if it so, forceUserdefinedcompaction or setting
> unchecked_tombstone_compactions to true wont help either as tombstones are
> less than 20% and not much disk would be recovered.
>
> It is not possible to add additional disks too.
>
> We see huge difference in disk utilization of different nodes. May be some
> nodes were able to get away with tombstones while others didnt manage to
> evict tombstones.
>
>
> Would be good to know more alternatives from community.
>
>
> Thanks
> Anuj
>
>
>
>
>
>
>
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