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From Robin Verlangen <ro...@us2.nl>
Subject Re: Disk configuration in new cluster node
Date Mon, 17 Sep 2012 08:25:47 GMT
" A word of warning. If you put more than 300GB to 400GB per node you may
end experience some issues  ... "

I think this is probably the "solution" to your multiple disk problem. You
could use easily one single disk to store the data on, and one disk for the
commitlog. No issues with JBOD, RAID or whatever. If you want to improve
throughput you might consider a RAID-0 setup.

Best regards,

Robin Verlangen
*Software engineer*
*
*
W http://www.robinverlangen.nl
E robin@us2.nl

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2012/9/17 aaron morton <aaron@thelastpickle.com>

>  4 drives for data and 1 drive for commitlog,
>
> How are you configuring the drives ? It's normally best to present one big
> data volume, e.g. using raid 0, and put the commit log on say the system
> mirror.
>
> will the node balance out the load on the drives, or is it agnostic to
> usage of drives underlying data directories?
>
> It will not.
> There is a feature coming in v1.2 to add better support for JBOD
> configurations.
>
> A word of warning. If you put more than 300GB to 400GB per node you may
> end experience some issues such as repair, compaction or disaster recovery
> taking a long time. These are simply soft limits that provide a good rule
> of thumb for HDD based systems with 1 GigE networking.
>
> Hope that helps.
> -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 15/09/2012, at 7:39 AM, Casey Deccio <casey@deccio.net> wrote:
>
> I'm building a new "cluster" (to replace the broken setup I've written
> about in previous posts) that will consist of only two nodes.  I understand
> that I'll be sacrificing high availability of writes if one of the nodes
> goes down, and I'm okay with that.  I'm more interested in maintaining high
> consistency and high read availability.  So I've decided to use a
> write-level consistency of ALL and read-level consistency of ONE.
>
> My first question is about the drives in this setup.  If I initially set
> up the system with, say, 4 drives for data and 1 drive for commitlog, and
> later I decide to add more capacity to the node by adding more drives for
> data (adding the new data directory entries in cassandra.yaml), will the
> node balance out the load on the drives, or is it agnostic to usage of
> drives underlying data directories?
>
> My second question has to do with RAID striping.  Would it be more useful
> to stripe the disk with the commitlog or the disks with the data?  Of
> course, with a single striped volume for data directories, it would be more
> difficult to add capacity to the node later, as I've suggested above.
>
> Casey
>
>
>

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