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From Pieter Callewaert <pieter.callewa...@be-mobile.be>
Subject RE: idea drive layout - 4 drives + RAID question
Date Tue, 30 Oct 2012 08:23:16 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

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<mailto: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<mailto: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<mailto: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<mailto: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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