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From aaron morton <aa...@thelastpickle.com>
Subject Re: idea drive layout - 4 drives + RAID question
Date Tue, 30 Oct 2012 19:58:52 GMT
> We also have 4-disk nodes, and we use the following layout:
> 2 x OS + Commit in RAID 1
> 2 x Data disk in RAID 0
+1

You are replicating data at the application level and want the fastest possible IO performance
per node. 

>  You can already distribute the
> individual Cassandra column families on different drives by just
> setting up symlinks to the individual folders.
There are some features coming in 1.2 that make using a JBOD setup easier. 

Cheers

-----------------
Aaron Morton
Freelance Developer
@aaronmorton
http://www.thelastpickle.com

On 30/10/2012, at 9:23 PM, Pieter Callewaert <pieter.callewaert@be-mobile.be> wrote:

> We also have 4-disk nodes, and we use the following layout:
> 2 x OS + Commit in RAID 1
> 2 x Data disk in RAID 0
>  
> This gives us the advantage we never have to reinstall the node when a drive crashes.
>  
> Kind regards,
> Pieter
>  
>  
> From: Ran User [mailto:ranuser99@gmail.com] 
> Sent: dinsdag 30 oktober 2012 4:33
> To: user@cassandra.apache.org
> Subject: Re: idea drive layout - 4 drives + RAID question
>  
> Have you considered running RAID 10 for the data drives to improve MTBF?  
>  
> On one hand Cassandra is handling redundancy issues, on the other hand, reducing the
frequency of dealing with failed nodes is attractive if cheap (switching RAID levels to 10).

>  
> We have no experience with software RAID (have always used hardware raid with BBU). 
I'm assuming software RAID 1 or 10 (the mirroring part) is inherently reliable (perhaps minus
some edge case).
> 
> On Tue, Oct 30, 2012 at 1:07 AM, Tupshin Harper <tupshin@tupshin.com> wrote:
> I would generally recommend 1 drive for OS and commit log and 3 drive raid 0 for data.
The raid does give you good performance benefit, and it can be convenient to have the OS on
a side drive for configuration ease and better MTBF.
> 
> -Tupshin
> 
> On Oct 29, 2012 8:56 PM, "Ran User" <ranuser99@gmail.com> wrote:
> I was hoping to achieve approx. 2x IO (write and read) performance via RAID 0 (by accepting
a higher MTBF).
>  
> Do believe the performance gains of RAID0 are much lower and/or are not worth it vs the
increased server failure rate?
>  
> From my understanding, RAID 10 would achieve the read performance benefits of RAID 0,
but not the write benefits.  I'm also considering RAID 10 to maximize server IO performance.

>  
> Currently, we're working with 1 CF.
>  
>  
> Thank you
> 
> On Mon, Oct 29, 2012 at 11:51 PM, Timmy Turner <timm.turn@gmail.com> wrote:
> I'm not sure whether the raid 0 gets you anything other than headaches
> should one of the drives fail. You can already distribute the
> individual Cassandra column families on different drives by just
> setting up symlinks to the individual folders.
> 
> 2012/10/30 Ran User <ranuser99@gmail.com>:
> > For a server with 4 drive slots only, I'm thinking:
> >
> > either:
> >
> > - OS (1 drive)
> > - Commit Log (1 drive)
> > - Data (2 drives, software raid 0)
> >
> > vs
> >
> > - OS  + Data (3 drives, software raid 0)
> > - Commit Log (1 drive)
> >
> > or something else?
> >
> > also, if I can spare the wasted storage, would RAID 10 for cassandra data
> > improve read performance and have no effect on write performance?
> >
> > Thank you!
>  


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