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From Elliott Sims <elli...@backblaze.com>
Subject Re: Cluster CPU usage limit
Date Fri, 07 Sep 2018 03:35:27 GMT
It's interesting and a bit surprising that 256 write threads isn't enough.
Even with a lot of cores, I'd expect you to be able to saturate CPU with
that many threads.  I'd make sure you don't have other bottlenecks, like
GC, IOPs, network, or "microbursts" where your load is actually fluctuating
between 20-100% CPU.
Admittedly, I actually did get best results with 256 threads (and haven't
tested higher, but lower is definitely not enough), but every advice I've
seen is for a lower write thread count being optimal for most cases.

On Thu, Sep 6, 2018 at 5:51 AM, onmstester onmstester <onmstester@zoho.com>
wrote:

> IMHO, Cassandra write is more of a CPU bound task, so while determining
> cluster write throughput, what CPU usage percent (avg among all cluster
> nodes) should be determined as limit?
> Rephrase: what's the normal CPU usage in Cassandra cluster (while no
> compaction, streaming or heavy-read running) ?
> For a cluster with 10 nodes, i got 700K write per seconds for my data
> model, average cpu load is about 40%, i'm going to increase number of
> native threads (now is 256) and native queue (1024) to increase throughput
> (and CPU usage subsequently).
>
> Sent using Zoho Mail <https://www.zoho.com/mail/>
>
>
>

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