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From Ryan King <r...@twitter.com>
Subject Re: Cassandra compaction disk space logic
Date Thu, 20 May 2010 00:20:08 GMT
2010/5/19 Maxim Kramarenko <maximkr@trackstudio.com>:
> Hi!
>
> We have mail archive application, so we have a lot of data (30TB on multiple
> nodes) and should delete data after a few months of storing.
>
> Questions are:
>
> 1) Compaction require extra space to process. What happend if node have no
> extra space for compaction ? Will it crash, or just stop compaction process
> ?

Stop compaction.

> 2) Is it possible to limit max SSTable file size ? I am worry about
> following situation: we have 1TB disk, 600 GB of data in single file and
> should delete 50 GB of outdated data. This can lead to another 550 GB data
> file generation, which cannot fit on the disk.

Not currently. You have to manage this operationally.

> 3) If we have 30 TB in data and replicas, how much disk space required to
> handle this, including adding new data, deleting old, compaction, etc ?

All of that depends on the cardinality of those operations (how much
is deleted, etc.). You're going to have to benchmark it.

> 4) What occurs, if we run decommission, but target node have not enough disk
> space ?

I don't know. Please let me know when you find out. :)

-ryan

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