Compaction in cassandra

[Akshit Jain <ak...@iiitd.ac.in>]

Is it helpful to run nodetool compaction in cassandra?
or automatic compaction is just fine.
Regards

RE: Compaction in cassandra

["Steinmaurer, Thomas" <th...@dynatrace.com>]

Hi,

usually automatic minor compactions are fine, but you may need much more free disk space to reclaim disk space via automatic minor compactions, especially in a time series use case with size-tiered compaction strategy (possibly with leveled as well, I’m not familiar with this strategy type). We are in the time series / STCS combination and currently plan to run a major compaction every X weeks. Although not perfect, this is currently our only way to effectively really get rid of out-dated data from disk, without the extra cost of storage we would additionally need, cause it needs a lot of time that delete markers (tombstones) according to our retention policy are actually getting automatically minor compacted with potentially large SSTables. Mind you, with pre 2.2, a major compaction results in a single (large) SSTable again, so the whole disk usage troubles start again. With 2.2+ there is an option to end up with SSTables in 50%, 25% etc.. in file size per column family / table, so this might be useful.

If you have a time series use case you may want to look at the new time window compaction strategy introduced in 3.0, but it relies on TTL-based time series data only. We tested it and it works great, but unfortunately we can’t use it, cause we may have different TTL/retention policies in a single column family, even varying retention configurations per customer over time, so TWCS not really an option here, unfortunately.

Thomas

From: Akshit Jain [mailto:akshit13124@iiitd.ac.in]
Sent: Donnerstag, 14. September 2017 08:50
To: user@cassandra.apache.org
Subject: Compaction in cassandra

Is it helpful to run nodetool compaction in cassandra?
or automatic compaction is just fine.
Regards

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Re: Compaction in cassandra

[Jeff Jirsa <jj...@gmail.com>]

Shouldn't need it under normal circumstances, and should avoid it unless you explicitly need it

-- 
Jeff Jirsa


> On Sep 13, 2017, at 11:49 PM, Akshit Jain <ak...@iiitd.ac.in> wrote:
> 
> Is it helpful to run nodetool compaction in cassandra?
> or automatic compaction is just fine.
> Regards
>