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From "B. Todd Burruss" <bburr...@real.com>
Subject Re: Effective allocation of multiple disks
Date Wed, 10 Mar 2010 17:03:18 GMT
with the file sizes we're talking about with cassandra and other 
database products, the stripe size doesn't seem to matter.  i suppose 
there may be a modicum of overhead with a small stripe size, but i'm not 
sure.  mine is set to 128k, which produced the same results as 16k and 256k.

i will say the number of drives within the RAID 0 setup does seem to 
matter.  more you have the more parallelism you can get with a good RAID 
controller.

Eric Rosenberry wrote:
> Based on the documentation, it is clear that with Cassandra you want 
> to have one disk for commitlog, and one disk for data.
>
> My question is: If you think your workload is going to require more io 
> performance to the data disks than a single disk can handle, how would 
> you recommend effectively utilizing additional disks?
>
> It would seem a number of vendors sell 1U boxes with four 3.5 inch 
> disks.  If we use one for commitlog, is there a way to have Cassandra 
> itself equally split data across the three remaining disks?  Or is 
> this something that needs to be handled by the hardware level, or 
> operating system/file system level?
>
> Options include a hardware RAID controller in a RAID 0 stripe (this is 
> more $$$ and for what gain?), or utilizing a volume manager like LVM.
>
> Along those same lines, if you do implement some type of striping, 
> what RAID stripe size is recommended?  (I think Todd Burruss asked 
> this earlier but I did not see a response)
>
> Thanks for any input!
>
> -Eric

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