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From Tyler Hobbs <>
Subject Re: READ messages dropped
Date Fri, 12 Oct 2012 20:48:21 GMT
On Fri, Oct 12, 2012 at 2:24 AM, Tamar Fraenkel <> wrote:

> Thanks for the response. My cluster is in a bad state those recent days.
> I have 29 CFs, and my disk is 5% full... So I guess the VMs still have
> more space to go, and I am not sure this is considered many CFs.

That's not too many CFs.  I don't know how much 5% of your disk space is in
absolute numbers, which is more important.  The most important measure for
whether you are approaching limits is really disk utilization (as in how
busy the disk is, not how much data it's holding).  OpsCenter exposes
metrics for this that you should check.

> But maybe I have memory issues. I enlarge cassandra memory from about ~2G
> to ~4G (out of ~8G). This was done because at that stage I had lots of key
> caches. I then reduced them to almost 0 on all CF. I guess now I can reduce
> the memory back to ~2 or ~3 G. Will that help?

I would leave your heap at 4G.  You really do want key caching enabled in
almost all circumstances; it can save you a lot of disk activity on reads.
If you need to bump your heap up to 4.5G to accommodate key caches, it's
worth it.

Tyler Hobbs
DataStax <>

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