RAC - Clusterd file system

Hi All,
This is very basic question but if you can shed some light. I have understanding that Clustered file system gives the ability to read and write same time for a file from multinodes. Is that true ? Can you pls. explain with an example ?
Please confirm if my understanding is correct -
For ( database related files and VOTING Disk and OCR )
Either we can use raw devices
Either we can use CFS ( any other or oracle given CFS )
ASM only for database files any of the above option for VOTING,OCR ..
Now back to orignal question - If we really need cluster file system so that both the nodes can access database files same time then how can ASM has this capability .. Is ASM another clustered file system ?
your response would be appreciated.
Thanks
Lyxx

coming to original questions: Basic concept for allowing concurrent read/write on a file is to allow the operations on block wise locking mechanism, while usual file systems takes file lock for read write. so in cluster file system two nodes can modify two different blocks (not the same).
ASM implements the same through its own locking mechanism, using lock manger processes and CRS architecture.
And its absolutely true that only one ASM instance will suffice for multiple DB but we can create multiple instances if needed (probably for better grouping/isolation of storage)
Experts please correct me if I am missing out on anything.
Thanks
Rajesh

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"some of us argue that oracle database has a built-in capability to decide on what level of RAID we store our data".
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Hi ,
Below link may be useful to you:
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Maybe this paper has: http://www.oracle.com/technology/tech/linux/pdf/Linux-FS-Performance-Comparison.pdf - it's a bit older, but explains some of the interdependencies.
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File system in 9i RAC

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Regards,
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Edited by: user12549343 on 02-feb-2010 9:10

You didn't provide info about DB relase and OS.
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I apologize for my english.
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