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From Alain RODRIGUEZ <arodr...@gmail.com>
Subject Re: lots of small nodes vs fewer big nodes
Date Thu, 08 Aug 2013 08:29:55 GMT
I advise you to have 7GB RAM better (more would be better if you have a lot
of data per node). But the real difference is made when you use SSDs or
RAIDs of SSDs, since the bottleneck is the disk throughput in most cases.

We are in the cloud, we tried a lot of configurations and were comfortable
only with a nodes RAM > 7 GB (RAM >15 GB with lot of data / node) and see a
real enhancement when we switched to SSDs (latency from 20-40 to 3-5 ms),
even reducing the number of nodes from 18 to 3. This was quite impressive
and I recommend SSD (or RAID of SSDs) since to anyone who can afford it.

Alain




2013/8/7 Andrey Ilinykh <ailinykh@gmail.com>

> You still have the same amount of RAM, so you cache the same amount of
> data. I don't think you gain much here. On the other side, maintenance
> procedures (compaction, repair) may hit your 2CPU box. I wouldn't do it.
>
> Thank you,
>   Andrey
>
>
> On Wed, Aug 7, 2013 at 10:24 AM, Paul Ingalls <paulingalls@gmail.com>wrote:
>
>> Quick question about systems architecture.
>>
>> Would it be better to run 5 nodes with 7GB RAM and 4CPU's or 10 nodes
>> with 3.5GB RAM and 2CPUS?
>>
>> I'm currently running the former, but am considering the latter.  My goal
>> would be to improve overall performance by spreading the IO across more
>> disks.  My currently cluster has low CPU utilization but does spend a good
>> amount of time in iowait.  Would moving to more smaller nodes help with
>> that?  Or would I run into trouble with the smaller ram and cpu?
>>
>> Thanks!
>>
>> Paul
>
>
>

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