[Ocfs2-users] ASM over OCFS2 vs. Standard locally managed tablespaces

[Luis Freitas]

Karim,

   I dont see why run ASM over OCFS2. It seems to be a useless overhead. Either you run ASM or OCFS2.

   Btw, neither ASM nor OCFS2 are smart enough to detect that some LUNs are faster than others. ASM expects each diskgroup to be comprised of LUNs of similar performance in order for it's load balancing algorithms to work. OCFS2, as far as I know doesnt have this type of management built in.

See:
http://www.oracle.com/technology/products/database/asm/pdf/take%20the%20guesswork%20out%20of%20db%20tuning%2001-06.pdf
Section: ASM Best practices and principals.

   About the performance, ASM is said to have similar performance to raw devices in a SAME layout, being tightly integrated to Oracle. OCFS2 has some overheads that are inherent to a file system, like cache management, locking, context switching, so it is likely to use more CPU power than ASM. But I dont remember any specific benchmark comparing those. 

    Also, keep in mind that when you use a filesystem you are using part of the memory for the filesystem cache. When using RAW or ASM you would need to allocate this memory to the block buffer in order to compare results.

Regards,
Luis

> Hello All,
>
>
>
> Are there any benchmarks with respect to performance with respect to  
> ASM over OCFS2 vs. standard locally managed tablespaces?
>
> In our environment, data files hosting tables/lobs are stored on a  
> RAID6 disk array with 10K rpm disks, whilst indices are  stored on a  
> different RAID6 disk array with 15K rpm disks.
>
> We’re using oracle managed files for the rollback/undo and temporary 
>  tablespaces.
>
> Would ASM over OCFS2 be smart enough to detect the fast LUNs?
>
>
>
> Appreciate your thoughts.
>
>
>
> Best regards,
>
> Karim
>
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