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From Peter Schuller <>
Subject Re: Limit on amount of CFs
Date Sun, 13 Feb 2011 10:40:21 GMT
> Reading in the documentation (specially on the tuning section) is clear the
> the number of Column Families affects the performance, in particular the
> amount of memory assigned to the heap.
> My question is: What's the hard limit on the number of CFs?
> Does anybody implemented an application with large number of CFs? if so,
> whats that number?

There's no meaningful hard limit as such that I am aware of, but the
idea is that you have few of them (meaning usually below 10 or so,
maybe more sometimes, but not hundreds or thousands).

The overhead associated is indirect in the sense that for a fixed heap
size, you'd need lower memtable flush thresholds per cf, leading to
smaller sstablers being flushed and thus leading to more compaction.

If you have so many memtables that you are worried about a hard limit,
you probably have too many of them already for reasons other than any
hard limits :)

/ Peter Schuller

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